It is unusual for a mathematical idea to spread through society. But this is the case with chaos theory, popularized by the butterfly effect, imagined by the American meteorologist Edward Lorenz, who in 1972 asked the famous question: “Does the flapping of a butterfly’s wings in Brazil trigger a tornado in Texas?” The idea in this picture is that a small cause can have big consequences. But can chaos theory be summed up in such a simplistic way? Can a scientific theory be satisfied with negative statements? Are mathematicians responsible for the inadequate transmission of this theory? This lecture will attempt to address these questions and, in particular, to describe the positive side of the theory. Because there is a positive side. Chaos sometimes creates a kind of order. Chaotic systems may be unpredictable, but they are far from incomprehensible.