It is not that often that I look at blood under the microscope. It usually happens when I get injured and have the opportunity to get a microscope. After an unfortunate shave, I act quickly so that I can prepare a slide from the blood before it dries up.

Diatoms are brown microalgae that can be found in all freshwater and marine environments. They are an important link in the ecological cycle. In streams and rivers you often see stones covered with a brown layer that is formed by diatoms.

Green masses in ditches and ponds are often caused by networks of long threads originating from filamentous algae.