Protists are a diverse group of eukaryotic microorganisms. Histo-rically, protists were treated as the kingdom Protista but this group is no longer recognized in modern taxonomy. The protists do not have much in common besides a relatively simple organization�either they are unicellular, or they are multicellular wthout specialized tissues. This simple cellular organization distinguishes the protists from other eukaryotes, such as fungi, animals and plants.