Tetraedron are single, free-floating cells classified as phytoplankton. They have a flattened shape, appearing triangular, quadrangular, or irregularly polygonal, with older cells becoming nearly spherical. The cell wall appears finely granulated under a light microscope. Each cell contains a single nucleus and a large chloroplast that occupies the entire cell volume, housing a single pyrenoid enclosed by a starch sheath. Reproduction in Tetraedron occurs asexually through autospores. Two, four, or eight autospores develop within the mother cell and are released when the parent cell wall ruptures. Zoospores and sexual reproduction processes are not observed in Tetraedron.