We can intuitively tell what makes a complex system with interacting components stable. For example in ecosystems, we know that the extinction of a prey species can lead to a mass extinction of predator species that feed on prey to sustain themselves, and genetic diversity helps organisms adapting to changing environments and rapidly evolving diseases. But is there a way to quantify stability with maths? When mathematicians speak about the stability of ecosystems, they usually refer to the asymptotic stability of an equilibrium point, characterised by the eigenvalues of a species interaction matrix. In reality, however, these interaction coefficients are difficult - if not impossible - to measure. Therefore in 1972, Robert M. May introduced a community matrix model, where coefficients are sampled from a random distribution, and derived a stability criterion based on the distribution of the eigenvalues using random matrix theory. For nearly 50 years, this model has been improved and applied in theoretical ecology.