Cyanobacteria /saɪˌænoʊbækˈtɪəriə/, also known as Cyanophyta, is a phylum of bacteria that obtain their energy through photosynthesis. The name "cyanobacteria" comes from the color of the bacteria (Greek:κυανός (kyanós) = blue). They are often called blue-green algae, although some consider that name a misnomer, as cyanobacteria are prokaryotic and algae should be eukaryotic.