Photomicrograph of a recrystalized mixture of anti-mucus medication and sodium citrate. A photomicrograph is simply an image that has been taken using a camera attached to a microscope. This particular photomicrograph was taken in polarized light. Typically, light waves vibrate in all different directions. When light is restricted to vibrating in just one plane, it is called "polarization" and this phenomenon can enhance certain features in such photos. (http://lightexhibit.org/bio_image31.html)