Matroids are basic combinatorial objects, abstracting the notion of linear independence. Despite the simplicity of their definition, they exhibit mysterious properties, some of which have taken mathematicians decades to prove. I will talk about a new facet of matroid theory that was revealed by thinking of matroids as high-dimensional expanders. This viewpoint revealed surprising connections with geometry of polynomials, the theory of Markov chains, and log-concavity and unimodality conjectures in combinatorics, and helped resolve two long-standing conjectures of Mihail and Vazirani, and Mason. I will also mention how subsequent works have built on this idea to resolve other major conjectures about mixing time of Markov chains.