The article explores chaos in various systems, from simple models to complex ones. It discusses how chaotic behaviors can be characterized and studied using a probabilistic approach. The researchers delve into chaos in dissipative and Hamiltonian systems, as well as its connection to information theory. They also touch upon chaos in few-degrees of freedom systems, spatiotemporal chaos, and turbulence. The study highlights the case of Fermi-Pasta-Ulam as an example of chaos in statistical mechanics.