MillerUrey

The Miller–Urey experiment was a 1952 chemical experiment conducted by Stanley L. Miller under the supervision of Harold C. Urey at the University of Chicago. The goal was to test whether key molecules essential to life could form from simple inorganic precursors under conditions thought to resemble the early Earth's atmosphere. The apparatus circulated water, methane, ammonia, and hydrogen in a closed system while an electric spark provided energy to drive reactions, emulating lightning. The vapor was condensed and recirculated. After several days, the mixture yielded several organic compounds, most notably amino acids such as glycine and alanine, demonstrating that complex organic molecules can arise abiotically from inorganic starting materials under plausible prebiotic conditions.

The experiment is widely cited as a landmark, helping to spark the field of prebiotic chemistry and origin-of-life research by showing a plausible pathway to the formation of life's molecular building blocks. Later work questioned the assumed reducing atmosphere of early Earth; more neutral atmospheres and different energy sources can still produce amino acids, though yields vary. The Miller–Urey experiment remains a foundational result for discussions of how chemical evolution could have preceded biological evolution.