Tetraedron trigonum is a genus of green algae known for its distinctive tetrahedral shape, resembling a triangular pyramid with four triangular faces meeting at a central point. Each cell is small, typically 10 to 20 micrometers in diameter, and enclosed in a cellulose-based cell wall. The algae contains disc-shaped chloroplasts for photosynthesis and reproduces through asexual cell division. It thrives in freshwater environments such as ponds and lakes, playing a role in nutrient cycling and serving as a food source in aquatic ecosystems.