It was believed that protein are the organic molecule which came first. Miller and Urey they used water, hydrogen, ammonia and methane and they generated spark just like lightning. They analysed the component in the solution after couple of days they found various organic molecules like amino acid which is the building block of protein. The simple organic molecule gave rise to larger structure. Some scientist also revealed that there are organic molecules which pass the genetic information from one generation to next generation, RNA was believed to be the hereditary molecule. various RNA was produced during the peroid of evolution and by natural selection best RNA were selected which could sustain environment changes. With time the organic molecules gave rise to prokaryotes then eukaryotes and the evolution goes on.