I will discuss the phenomenon of collapsing for sequences of Riemannian manifolds whose volume tends to zero while curvature remains uniformly controlled, with particular emphasis on lower Ricci curvature bounds. Understanding the topology and metric structure of the limit spaces, and their relation to the original sequence of manifolds, is a subtle question that has attracted a great deal of attention over the years. I will begin with a brief overview of classical results in the setting of sectional curvature bounds, and then turn to the Ricci framework, including Ricci limit spaces and their synthetic counterparts. In contrast with the sectional curvature setting, collapsing under nonnegative Ricci curvature is much more flexible and can produce wilder limit spaces. I will conclude with a recent joint result with Qin Deng on the topological structure of two-dimensional collapsed limits. Most of the talk will be based on examples.