Monera (/məˈnɪərə/) (Greek - μονήρης (monḗrēs), "single", "solitary") is a kingdom that contains unicellular organisms with a prokaryotic cell organization (having no nuclear membrane), such as bacteria. They are single-celled organisms with no true nuclear membrane (prokaryotic organisms). Most bacteria were classified under Monera; however, some Cyanobacteria (often called the blue-green algae) were initially classified under Plantae due to their ability to photosynthesize.