Earth – the blue planet: lots of water-lots of algae-lots of oxygen. The most important and oldest single cell plants on earth “The Algae” and the very reason of our existence. These single cells carry lots of secrets and many of them are still unknown to us though they played important roles in the evolution and development of life on earth. They have micro- and nano- devices with complex molecular structures and diversity of biochemical metabolic reactions, e.g. photosynthesis and nitrogen fixation, production of amino acids and lipids. Algae with thousands and thousands of species can be very small or very large in size with different colors and can be useful or harmful. Algae remains, diatoms, can be preserved in sediments for millions of years. The most important is that algae are the origin of gas and oil and recently that algae can be used for production and a source of biofuel!