You probably have never heard of them before, but without cyanobacteria none of us would be here. Cyanobacteria helped “fix” nitrogen into nitrates, nitrites, and ammnonia. They increased the oxygen level. High levels of oxygen eventually created an extinction event that forced organisms to adapt. The second part why Cyanobacteria are amazing is because they appear to have become chloroplasts. How can we now such things? First, they have their own DNA (and so do mitochondria). They also share many genetic and physical characteristics. This is actually what happened with mitochondria too. The oxygen we breath, the nitrogen we need, all living organisms that require oxygen would not be here if it wasn’t for cyanobacteria.