Search for the origin of life on the earth is one of the most fascinating and popular subjects in the field of natural sciences at present. We have a big question: where we human came from and how life originated on the earth. Life is not a spectacular miracle but rather a chemical inevitability that is probably occurring elsewhere in the universe. The sun and planets of the earth's solar system formed about 4.6 billion years ago and life originated spontaneously in the process of chemical evolution in the range of 4 to 3 billion years ago. Until very recently ribonucleic acid (RNA) was considered to be a passive carrier of information stored in the DNA. The demonstration within the last few Years that RNA can have self-catalytic activities, is changing its image. In particular, recent new results strongly support the hypothesis that RNA, not DNA, was the first carrier of information and had the capacity to replicate itself in the absence of protein enzymes. We have been challenged to solve the riddle of life's origin and succeeded reconstruction of the many events associated with the origin of life on the earth. In this article we summarized our view on the origin of life on the earth, introducing human understanding about the origin of life from ancient times up to the present time and the characteristics of life, and examining the construction of protocellular structures, nucleic acids, and polypeptides under possible primitive earth conditions. In addition, we discussed a RNA world, a key step in the genesis of life, in which RNA self-replicates itself.
