Light micrograph of a rock thin section of Gunflint cherts from Ontario, Canada, showing fossil remains of the earliest life forms yet found, dating from two billion years ago. The sample includes a mixture of organic detritus, filaments resembling the modern day filamentous blue green algae, colonies of algae (spikelets) & spheroids associated with current coccoid blue green algae. These primitive plants gained energy through photosynthesis, releasing free oxygen into the environment as a by product. This had far reaching consequences for the subsequent history of the environment. Mag:X400 (35mm size).