Since the epidermal cells are purple and the stomata have chloroplasts that make them green, they are relatively easy to see. The easiest way to observe stomates is to use a whole Zebrina leaf. Choose your plants well, though. Some are much more obliging than others. Magnolia, for instance, separates easily, whereas oak does not.
Geraniums are usually most accessible and are easy to work with.
I advise the kids to clean their slides, put a droplet of water in the center, and have a razor blade handy. Next, the razor blade can be used to cut away the rest of the leaf. Add a cover slip and voila. This entire site protected by copyright. All rights reserved.