Oxygenic photogranules is a new type of biogranules that has promising bioengineering applications to wastewater treatment, but how they are produced by the filamentous and motile cyanobacteria (also known as the blue-green algae) from a source of activated sludge exposed to light is still far from understood.
OPGs were discovered recently and serendipitously in laboratory conditions, but very similar granules, called cryoconites, are found in glaciers 
