Micrasterias as seen under a light microscope. Micrasterias (order Desmidiales) is a unicellular green alga found in fresh water, which varies in size depending on the species and may reach up to hundreds of microns. Micrasterias species consist of two semicells that are almost entirely filled with chloroplasts, with a nucleus that lies at the center, where the two semicells are joined together. The gaps between the two semicells are joined by an isthmus (information and image retrieved via Wikimedia/Wikipedia; image by Ajburk; the image was modified by MIC). The cover is published under the Creative Commons Attribution (CC BY) license.