In 1953, Stanley L. Miller and Harold C. Urey, working at the University of Chicago, conducted an experiment showing that organic compounds such as amino acids, which are essential to cellular life, could be made easily under the conditions that scientists believed to be present on the early earth.

The gases they used were methane (CH4), ammonia (NH3), hydrogen (H2), and water (H2O). They ran a continuous electric current through the system, to simulate lightning storms believed to be common on the early earth. Analysis of the experiment was done by chromotography. At the end of one week, they observed that approximately 10-15% of the carbon was now in the form of organic compounds. Two percent of the carbon had formed some of the amino acids which are used to make proteins.