#unicellular algae

• Diatoms — A class of microscopic unicellular or colonial algae, scientifically known as Bacillariophyceae or commonly as diatoms, characterized by a silicified, rigid, and ornamented cell wall called a frustule, consisting of two overlapping valves like a box. These aquatic photosynthetic organisms play a fundamental ecological role as primary producers in the phytoplankton of seas and fresh waters, with their fossil accumulations forming diatomite.