Leptodora kindtii is the biggest waterflea. The image is a photomontage of several images since the organism was too big for the microscope. This is a male of 5 millimeter. Females can become almost 2 centimeters long. These predators hunt on other waterfleas. They are completely transparent apart from the large eye.
Desmids like this Micrasterias rotata are amongst the most beautiful microscopic organisms. They are conjugating green algae.