According to modern ideas, the first step in the origin of life was

the formation of simple organic molecules   
In the most popular Miller-Urey experiment, the most living organisms were first developed under the formation of the simple macromolecules that composes most organelles in the cells of a living organism. It started with the gases –methane, ammonia and hydrogen which came in contact with electric spark that aided the first formation of the basic components like amino acids, nucleic acids and RNA. Then resulted to the development of prokaryotes or the autotrophs.