Edward Lorenz - Wikipedia

Edward Lorenz, a research meteorologist at MIT., Lorenz observed that that minute variations in the initial values of variables in his primitive computer weather model (c. 1960) would result in grossly divergent weather patterns. This sensitive dependence on initial conditions came to be known as the Butterfly effect.

He went on to explore the underlying mathematics and published his conclusions in a seminal work in the annals of chaos theory, Deterministic Nonperiodic Flow in which he described a relatively simple system of equations that resulted in a pattern of infinite complexity, the Lorenz attractor