Diatoms are a type of microscopic algae found in both freshwater and marine environments. They are unique because their cell walls are made of silica, which forms intricate and beautiful patterns. These single-celled organisms play a crucial role in the ecosystem, as they produce oxygen through photosynthesis and serve as a primary food source for many aquatic organisms. Diatoms are classified within the group of phytoplankton, which includes other microscopic plants. They are essential for the global carbon cycle, as they absorb carbon dioxide and help regulate climate. Their fossilized remains contribute to sedimentary rock formations, making them important in geological studies and paleontology.