False colour transmission electron micrograph of the blue-green algae, Spirulina platensis. Here, a single cell of this species is seen. Blue-green algae (cyanobacteria) are primitive algae. Their internal structure is closely related to bacteria. They are prokaryotic organisms which contain no membrane-bound nucleus; instead, as in bacteria, their nuclear material is dispersed throughout the cell. Photosynthetic lamellae (thread-like structures) are the primitive equivalent of chloroplasts. The red spots are food reserves known as cyanophycin granules. Some Spirulina species are eaten as a protein-rich health food. Magnification: x6660 at 6x4.5cm size.