The Cells Alive! website is a great resource for biology teachers and home educators covering cell biology.
One of the most unique features of this site — which can be used for elementary through college students — is the How Big? interactive. Zoom in to see the relative sizes of a pin head, a human hair, a dust mite, and various bacteria and viruses. This really gives people of all ages a solid understanding of just how small these microscopic objects are! Measurements are provided in millimeters, then micrometers and finally nanometers.
There are 4 sections on the Cells Alive! website, each with links to their various interactive features:
While much of the details on this site can really only be useful to high school or college level students, a few animations and interactives are helpful for even young children – like the How Big? interactive mentioned above.
If you use the Cells Alive! website — or would like to recommend a similar resource — please leave a little feedback below – thanks!