This is a picture captured from the Ken-A-Vision digital microscope that I use in my classroom. The image is from a wet-mount slide of Lactuca sativa (iceberg lettuce). The lettuce has been magnified 400X. Pertinent structures are labeled, including guard cells and stomatal units.
The beauty of this image, as well as the others I've uploaded, is that it shows what students will see when looking through their own compound light microscopes. Rather than trying to connect an edited, color-corrected, (super) high definition image from the internet to what students are seeing in their own scopes, you can give them a far more usable, relatable, teachable image to work with and learn from.