Teaching Microscopy to Young Children
While there are books published on teaching microscopy to children and young adult beginners, e.g. Teaching Microscopy, ed. by John Delly, Microscope Publications (1994); and The Private Eye: (5x) Looking/Thinking by Analogy, by Kerry Ruef, Skylight Professional Development (1998), they are generally written for teachers with an older group of children, perhaps 5th grade or higher, and often without actual hands-on experience with a microscope. It is assumed that children younger than that, or in the first decade of life, lack the attention span, reading skills, and dexterity to handle the subject matter. It is the experience of this author that not only is it possible to introduce K–4 children to microscopy, but using the right approach, it is an activity that engages and excites younger children, and is an unparalleled general introduction to science. This article will outline a successful teaching technique used repeatedly and successfully with K–2 students, most of whom have never touched or looked through a microscope.
Rather than beginning with a list of the equipment and materials required, perhaps it would be better to simply tell the story of my actual experience, and outline the basic strategy and methodology for teaching young children. I had no previous teaching experience or formal training working in an educational situation with children that age. So, faced with the challenge of doing this with a group of as many as 24 children at a time in an urban summer camp setting, and having no model “lesson plan” to work with, considerable imagination and experimentation was called for to develop a program from scratch.
I was very aware that children that age cannot sustain attention long enough for any sort of lecture, and that they need to become engaged almost immediately, using their eyes, brains, and fingers. That became my first challenge. I wanted to use familiar objects to grab and hold their attention, and then within 10 to 15 minutes, get them doing something with their hands. What I settled on was this:
As the children file in and take their seats, eight to a table, a video of ants in a Petri dish, crawling over and around a penny, is projected on a screen in the front of the room (Figure 1).
“What are these?” I ask the children. “ANTS!” They all shouted.
“How did they get so big? I thought ants were little, tiny things.”
“You made them bigger with a microscope,” the kids volunteer, not a bad guess, given that on the desks by each child was a microscope.
A comment here: I learned early on that children that age do not share very well, and are not patient enough to wait their turn. So one ‘scope per child is an important requirement. I have acquired enough beginner microscopes to equip a classroom for 24 students, and transport these scopes within light-weight home-made cases made of hardened styrofoam. (See the author’s article about these cases: “Making a Clamshell Case of Hardened Styrofoam for the Beginner Microscope.”) These lightweight monocular microscopes (Figure 2) and custom-made cases make transport much easier, and classroom setup does not involve any AC wiring—they are all battery operated, with LED light sources.
“Well, if I put YOU under a microscope would you get any bigger?” Laughter. “OK, so it’s not really the ANTS that are bigger. So what is?”
“The PICTURE of the ants,” someone usually volunteers. “OK, we call that an IMAGE. But HOW MUCH bigger is the image than the real ant?”
Here there comes a gaggle of responses: “A hundred times bigger—a thousand—a million!”
“Well, let’s find out.” I had previously made a line of thirty pennies, arranged in a single row, edge to edge, and held together with clear Scotch® tape applied to the top and underside of the row. “Who can count? How many pennies do I have here?” One smart kid raises his hand, and counts out the pennies to thirty. I announce this to the class, and then I hold up the string of pennies to the middle of the penny on the video on the screen (Figure 3).
“So this penny image is thirty times bigger than a real penny, right? So how much bigger are the ant images to real ants?”
“Thirty times bigger!” a chorus of kids yells out.
“So we have magnified the image of the ants thirty times, right?” “YES!”
Thus, the concept of image magnification is intuitively introduced to kids who know nothing more about mathematics than how to count to thirty, which most of them can do from watching Sesame Street®.
The next step is to introduce them to focus, which I do with a 10X jeweler’s loupe magnifying glass. Each child has one at his desk, along with a penny. I ask them to look at the penny and see if they can find the little man in between the columns on the building on the back of the penny (it is an image of the statue of Lincoln at the Lincoln Memorial in Washington, D.C., which is about 0.5 mm, Figure 4).
At this point the kids need a little help, and I have had the good fortune of having “camp counsellors” assistants, one per table; I find that this is absolutely essential. It is not possible for one teacher to handle more than eight students at a time, and 24 students is the absolute maximum I find it possible to manage at one session—with assistance. But the kids do have fun finding the “little man” on the penny, and in the process they learn that to see him clearly they must FOCUS the lens, holding it not too far away or too close to what they are looking at.
When everyone has found the seated Lincoln figure, I call their attention to a tubular object I am holding. It is a single telescoping tube with a lens at each end, similar to the historical one that is credited to the 16th century Dutch optician, Janssen. I use an inexpensive pocket ‘scope for this, available on eBay for less than $10. I explain that looking through it from one end it works like a spyglass, or telescope, and from the other, it is a microscope (Figure 5).
I pass several of these around for the kids to have a look at. While they are doing that I pick up a microscope and point out that this is just a more complex version of that tube, but still consists of a tube with lenses at both ends, and a few other parts that make it easier to use—and thus begin the naming of the eight parts of the microscope, and what they are for: eyepiece (the piece closest to the eye), objective (the lens closest to the object you are looking at), the body tube separating them, the stage (where all the action takes place), the focus knob, base, arm, and substage light. After each item I have the kids say the names, and then I run through it again asking what the name is of each part I point to. They sometimes need a little help, but overall they get it. I also have a wall chart that shows a simple monocular microscope with the parts named.
“So now, how do we get the actors on the stage—or what we call specimens? Let me show you how easy that is. Microscope people usually put specimens on a glass slide—and we call it that because we can slide it around on the flat stage to look at it.” I show them a glass slide. “Glass can break, but there are other ways to make slides. Would you like to learn how to make a slide yourself?” “YES!”
Here I use another piece of equipment that I find essential for teaching kids—an Elmo presentation tablet which can be connected to a projector. I should mention here that in the setup at the front of the classroom for projection of the ant video I have a laptop computer connected to a small projector. The Elmo attaches to this projector, and I can easily switch from the laptop to the Elmo with the press of a button on its remote controller. Now I can project an image of my hands doing things on the Elmo tablet.
What I show the kids at this point involves a custom-designed business card with a pattern on the back (Figure 6). At each child’s workspace is a Ziploc® plastic bag with several items in it: a child’s scissors, hole-punch, and roll of completely transparent Scotch tape. With the Elmo projector I show the kids how to cut off the X’d-out ½” squares at one end of the business card, then cut it down the middle lengthwise. This makes a small cardboard 1″ x 3″ slide. Next, I have them punch out three holes where the circles are, and put a piece of Scotch tape on the back side. I have them do this with both slides made from a single business card form.
The next order of business is to get something on the slide, and for this purpose I have three Petri dishes at each table: one with a small quantity of ordinary beach sand, one with table salt, and one with sugar. I start with the sand, and show how to press the business card slide, sticky side down, on top of the sand, press it lightly, and then pick it up and shake it gently over the dish. The children have now made their first slide out of very basic, safe materials—and now it is time to see what that looks like under a microscope.
Here I should say something about what I have found to be the ideal introductory microscope for children (Figure 2). There are several versions from different manufacturers of this basic ‘scope, but the minimal requirements I have found are these: sturdy monocular construction, made of light but sturdy metal; standard lenses—10X WF eyepiece and three achromat objectives, 4X, 10X, and 40X, of sizes and threading interchangeable with any standard laboratory microscope; three-position rotating nosepiece; coarse focusing adjustment; stage clips, but no mechanical stage; battery-operated twin LED light sources above and below stage.
Most of these ‘scopes come with a substage rotating disk with various size holes substituting for an iris diaphragm, and some have a fixed stage lens acting as a condenser. I have found the dual light source invaluable for teaching purposes, as will be obvious from the next section, but a small and inexpensive LED flashlight can be substituted for the upper light source if that is lacking, and is almost as effective.
I should also note that for children, monocular microscopes are much better than binocular head ‘scopes, because children that age have difficulty adjusting the binocular tubes to fit their interocular distance, and getting both eyes focused properly is often difficult. Some children wear glasses, and this presents another problem easily resolved with a monocular microscope.
So, having made their first DIY microscope slide, the kids are anxious to see what sand looks like under the microscope. All the ‘scopes are set up before the children arrive, with a plastic slide with a printed letter “e” pasted on it, cut from a computer printout. The lowest power objective is in position and focused, and all the child must do is turn on the microscope light and look—and possibly focus it a little. One-on-one supervision is sometimes required, but a little experimentation by the child is harmless and exciting.
With that, we switch slides to the DIY one they just made, and get them to see the sand grains at low power, with substage illumination. After they have had a chance to move the slide around, focus, etc., we then get them to switch from substage to “epi” illumination. On the ‘scopes I use (described above), that is accomplished by a flick of the toggle switch on the base of the ‘scope. This leads to shrieks of delight as the kids discover that the epi-illumination lets them see what the grains actually look like on the surface—their shape and color—in a way that is not visible with the substage illumination.
Next, we have the kids make DIY slides using the table salt in the second Petri dish, and here they get to see the geometric cubic shape of salt—the beginning of mineralogy—as well as being able to see through the crystals to bubbles and such inside the salt grains.
This is followed by doing a table sugar slide, and this is an opportunity to show them what polarization microscopy is all about. I had previously glued a small (1 cm) polarizing disk on the rotating substage “iris” disk, in the position of the second largest hole. I have also made a set of caps to fit over the top of the eyepiece, with a second polarizer glued over a hole in the center. By rotating the substage POL disk they get a polarizer in position; and then by rotating the POL eyepiece “analyzer” cap they watch as the background field goes dark and the sugar crystals suddenly display “rainbow colors.” They find this very exciting, and we suggest trying to do this with the salt, which does not show the same birefringent quality. (We don’t use the word, of course—but why not? Kids that age love big, ugly words; think supercalifragilisticexpialidocious.)
All this takes up perhaps 1-2 hours. Part of the next hour is taken up looking at prepared slides I have at each table—all of them made with plastic slides—of feathers, cat hair, lily pollen, fibers from a clothing dryer, and other odds and ends. One that engages them is a “FIND THE ANT!” slide, where I placed a dead ant in one of the three holes in a DIY slide, each hole labeled “1,” “2,” or “3” (Figure 6, bottom). When the child finds the ant, he or she gets a reward (I have used blowing bubbles from a hobby wedding bubble bottle, but other rewards are limited only by imagination of the assistants, who are usually not short on ideas). Children are also encouraged to try to make drawings of what they see, with small pads of paper and pencils at each table.
The last few minutes are devoted to kids seeing two different microscope items. The first is a slide I made of a banana vein from an ordinary peeled banana. It is wonderful for showing the spiral tracheids inside a tubular vein, but I have an interesting way to introduce this phenomenon. I bring to class a Slinky® toy, and stand before them rocking it from hand to hand (Figure 7).
“What’s this?” I ask.
“A SLINKY!” They all shout in unison. (I have yet to meet a child – or adult for that matter – who does not know what a Slinky is; it is pretty close to being a universal toy.)
“Supposing I told you that you EAT SLINKIES!”
There is a loud gasp that passes through the room.
“Well, I don’t mean a big metal Slinky like this one, but supposing you ate tiny Slinkies without knowing it, in bananas, celery, pineapple… in fact in just about every fruit and vegetable you eat? Here—line up and I will show you one from a banana.”
At this point, I have half the kids line up here, and the other half before a second table which I will describe in the next section. On the first table I have a two-headed microscope—this one actually an inexpensive Ken-A-Vision two-headed monocular ‘scope that is not essentially different than the ones the kids have been using at their tables. I focus on the banana vein spiral tracheid, and have the child look at the same thing from the second viewing tube. I sometimes have to focus up and down a bit for them to see the spiral tracheid, but virtually all of them have no trouble seeing it (Figure 8).
I also have prepared a wet-sample slide with rotifers on it—from a culture I have been keeping going for over five years. These are good-sized bdelloid rotifers, and fun to look at. I have one of the assistants sitting at a table with a second two-headed monocular microscope, and that one is equipped with a mechanical stage to make it easier to find and track the rotifers. The kids get excited seeing living microscopic “animalcules” actually swimming around (Figure 9).
I should confess here that usually it is an assistant at the Slinky table, and I am at the rotifer one.
One other activity I have used with children, if there is enough time, is to “make your own lens.” For this exercise I use the clear glass beads sold for flower vase arrangement. They are generally sold as hemispheres about 1.5 cm in diameter, with a smooth and polished upper lens curvature, but an irregularly-surfaced flat bottom—the basic geometry of a plano-convex lens. The objective is to show the kids how glass can be polished smooth, and that this how lenses have traditionally been made for centuries. To accomplish this, I prepare in advance four pieces of sandpaper of decreasing grit size. Each sandpaper sheet is approximately 4″ x 5″, and they are numbered sequentially 1–4. I also have for each child a sand hourglass egg-timer—which takes about one minute to drain top to bottom, and can be flipped. We show the children how to hold the glass bead flat side down on the rough side of the sandpaper strip held on a flat desktop. Then we show how to start timing by turning the hourglass timer upside down, and start rubbing the bead in circles, back and forth, up and down, etc., on the sandpaper. After the hourglass minute timer has emptied, they move to the next finer grit sandpaper, and start over again. This continues through the four sheets, and at the end, the flat side of the glass bead is very smooth—but has a ground glass appearance that renders it opaque. Total polish and clarity is not really possible in this setting, so as a final step, one of the assistants paints a very thin layer of clear fingernail polish on the surface of the flat side of the bead, and places it on the table to dry. Once it is completely dry (in just a couple of minutes), the child can look through the bead as a small magnifying lens—and take it home to show friends and family.
What this exercise shows is a number of things—primarily the basics of what is involved in abrasive lens grinding, but it also focuses the children on a succession of connected ideas about uniform sand flowing (the hourglass), sand abrasion (the sandpaper rubbings), and, in general, glass lenses—which are made from sand! This also brings them full circle back to the sand they started out looking at.
CONCLUSION AND SOME FINAL COMMENTS
What I have described here is a simple procedure I have repeatedly used in a classroom or general meeting area to introduce groups of K-4 children to the essentials of microscopy: magnification, focus, single lens and compound microscopy, the parts of a compound microscope, simple slide making, substage and epi-illumination, simple use of polarization in microscopy, and seeing a variety of microscopic objects including sand, salt, sugar, hair, feathers, fibers, microscopic plant structures, and living microscopic animals. In addition, the child may learn about how lenses are made and polished, and the joys of seeing and doing things by themselves. At each table there are paper tablets and colored pencils, and the children are encouraged to try to draw or make sketches of what they see in the microscope. There is also a separate table with several stereo-“dissection” microscopes and specimens of small insects embedded in acrylic plastic. Children are encouraged to move around and share with each other what they are seeing and doing.
While this discussion has been about my experience teaching K–4 children, I have modified the procedure somewhat and adapted it for teaching 6th grade children in a different program setting. For that occasion, the introductory methods and materials were somewhat the same (e.g. use of the ant video, jeweler’s loupe, DIY slide making, etc.) but abbreviated and accelerated in order to get to a more-defined subject matter, which was the main focus for the day’s session. That topic was “soil” in an overall ecological context, so the microscopy was subordinated to that overall subject matter. It was also adjusted for the more mature level of the students, who needed less guidance and supervision by the teacher and assistants. Our experience on the one occasion (so far) that it was used is that it generated an equivalent level of interest and excitement by the participants. Both the K-4 and 6th grade experiences were carried out under the aegis and sponsorship of the Evanston Ecology Center, of the City of Evanston, Illinois, and occurred at their sponsorship of a summer camp program in ecology during 2014, 2015, and 2016.
At the end of the class session, I ask them to raise their hand if they had fun; “YES!” Is always the answer. As the kids line up to leave, I have each of them gather up their DIY slides and lens to take home and show to their parents, guardians, and friends. I also suggest that they ask for a microscope for their birthday or other holiday, one similar to the ‘scope they used today. I have copies of a sheet with information about microscope sources, prices, and availability ready for them to take home.
I have used these techniques for several years running with a total of over 150 children in the K-4 age range, and it seems to be remarkably successful. One of the counselors told me that when asked what their favorite summer camp activity had been, most of the children said “the microscopes!” I have no idea at all if any of the children or their parents have followed up with microscopy, but I feel strongly about the need to “plant the seed”—hoping it will germinate, if not in a science career, in a wonderful hobby—and perhaps a lifelong learning interest in science and microscopy. Above all, the seed I want to plant is that children can and should see for themselves, and not just learn from second-hand or adult-mediated things like TV, computers, cell phones, magazines, and such. I am dedicated to making that happen as often as I can, and with as many children as possible.