What is Diatoms?
Bacillariophyta are commonly known as diatoms because of their unique structure. These unicellular photosynthetic organisms are composed of two overlapping glass shells that fit together the way old pillboxes did, with one shell fitting inside the other. These microscopic diatoms have distinctive markings, or ornamentation on their shells. Their natural symmetry is visually astounding when viewed under the microscope.
There are two major groups of diatoms, divided on the basis of cell symmetry. The centric diatoms have radial symmetry, oriented around a mid-point much like a wheel and hub, as seen at the left.