What was the experiment of Stanley Miller (1953) on the origin of life?

In 1953 the Stanley Miller arranged an experimental apparatus that simulated the atmospheric conditions of the primitive earth. The experiment contained a mixture of ammonia, methane, hydrogen and circulating water that when heated was transformed into vapor. He submitted a mixture to continuous bombardment of electrical discharge and after days obtained a liquid residual within which he discovered organic molecules and among them surprisingly the alanine and amino acids glycine, the most abundant constituents of proteins. Other researchers imitate the Miller experiment and noted also the formation of other organic molecules such as lipids, nucleotides and carbohydrates.