Diatoms are microscopic algae composed of separate halves, with delicate siliceous cell walls. They're usually single-celled organisms, though some live colonially. They inhabit fresh and salt waters and are among the most abundant of all phytoplankton.
Two interphase cells with immunofluorescence labeling of actin filaments (purple), microtubules (yellow), and nuclei (green). This image won first place in the Nikon 2003 Small World photo competition. The Cell: An Image Library - Image
frontal-cortex: Scanning electron microscope picture of a nerve ending that has been broken open to reveal the synaptic vesicles beneath the cell membrane. Image by Tina Carvalho. The Cell: An Image Library