A hypothesized mechanism for the origin of life, an event called abiogenesis. In this version, called RNA world, small molecules called nucleotides formed in the waters of the early Earth during the Hadean Eon, and polymerized on the surface of clay minerals. These simple chains of RNA could replicate themselves in solution, but only slowly and inaccurately. An RNA molecule developed which would fold into a structure that catalyzed RNA polymerization; a ribozyme. The first ribozymes would replicate their sister strands, and produce copies of themselves and other RNA molecules.
In the same environment, long chains of carbon molecules called phospholipids were formed. These molecules have two parts, the tail, which is hydrophobic, and the head, which is hydrophillic. Because of these properties phospholipids will stick together and form micelles and vesicles in water. Vesicles can absorb RNA nucleotides, concentrating them and creating a space where they can replicate, mutate and evolve. At some point a ribozyme became enclosed within a vesicle, starting a chain reaction that evolved into the multitude of biological forms that we see today.
Because this event occurred more than 3.8 billion years ago, theories about how and where it happened are highly speculative. Possible environments for abiogensis include hydrothermal vents on the ocean floor, hyper saline bubbles of water trapped in ice, radioactive lakes or lagoons on earths surface, and even in space or on another planet, brought to earth through a panspermia event. We have very little molecular evidence of the first cells, but ribozymes and catalytic RNA molecules are embedded in the DNA replication machinery of all life. Because evidence of this event has almost certainly been lost to time, the true mechanisms of the origin of life may remain a mystery to science.