Fossil blue-green algae.
Another image from the Nikon small world photomicrography competition, winning 5th place in 1993, depicts a fossilised section of the type of organism that gave the world free oxygen three billion years ago or more. Without these life-forms, who incidentally are not algae but cyanobacteria, none of life as we know it would exist. The oxygen from these first photosynthesisers first filled the oceans, resulting in the banded iron formations from where we mine that metal, and then the atmosphere, paving the way for the rise of oxygen using marine and terrestrial life. In the process, they incidentally poisoned off most of the existing ecosystem, since it couldn’t tolerate free oxygen. They survive as what we now call extremophiles.
The magnification is 10 times, and the lighting used that known as brightfield, which is direct illumination from below the sample.
Image credit: Norm Barker