Tetraedron minimum, a species of green algae, is characterized by its small, tetrahedral or pyramidal-shaped cells, typically ranging from a few to several tens of micrometers in diameter. The cells have smooth and robust cell walls, often thickened at the corners or vertices of the tetrahedron. Each cell contains a single parietal chloroplast with pyrenoids for photosynthesis and starch storage, along with a centrally located nucleus. The cell apices or corners are prominent, sometimes appearing slightly extended or pointed. These distinctive morphological features define Tetraedron minimum within the green algae family.