How the life were created on earth is an interesting question, but there is no definite answer. It is assumed that nearly billion years ago this world was inhabited by prokaryotic organisms. Among them, a type of prokaryote was able to trap the solar energy and used to produce glucose. Second type used to able to break the glucose to produce energy and the third type used to get energy by consuming substance from the surrounding. Both the first and second type of cell were lack of specialised cell organelles and in the way of evolution took shelter in to the third one.