Prochlorococcus and Synechococcus are single celled cyanobacteria. They are the smallest yet most abundant photosynthetic microbes in the ocean. They are so small that a hundred of these organisms can fit end-to-end across the width of a human hair and there are around 100 million Prochlorococcus cells per litre of seawater. Researchers estimate that Prochlorococcus and
Synechococcus