Daphnia magna is an almost-microscopic, transparent, fresh-water crustacean that looks something like a very intelligent, infinitesimal shrimp. But for medical researchers Daphnia has other charms ...

This is a mature Daphnia magna imaged under a microscope at 20x magnification. The photo was taken at the end of the 21 day exposure to sunscreen so that we could measure its body length. The black ...