In the beginning, only a few microorganisms existed on our blue planet, adapted to metabolize the then atmosphere of ammonia, carbon dioxide, nitrogen, methane and sulfur gases. Plants and animals as we know them today could only develop when a special form of photosynthesis was “invented” by cyanobacteria, so-called blue-green algae: More than two billion years ago, blue-green algae thereby enriched the original atmosphere with molecular oxygen (chemical: O2). Through their particularly efficient photosynthesis, these microorganisms still convert carbon dioxide from the atmosphere into sugar with the help of sunlight energy and the consumption of water, and produce oxygen as a waste product. For many organisms at that time, the new oxygenated atmosphere was toxic, while others adapted to the new living conditions and changed fundamentally over the years. Without O2, such complex and large creatures as we humans would not have evolved. Therefore, the emergence of O2-producing photosynthesis was the beginning of our life on Earth today, and without algae and plants, animals and humans would not survive.