It was proposed by Francisco Redi and Louis Pasteur. According to this theory life arose from pre existing life. Redi practically proved that life never arose from non living matter. Maggots will arise from decaying organic meat if it contains eggs only. If eggs are absent on such meat, never maggots will arise.
Even though biogenesis explains the formation of living organism from pre existing life, it never explains the origin of first living organism. But it laid the foundation for proposing the theories of organic evolution.
The different steps in the formation of first living organism are explained below.