Galaxy clusters are the largest relaxed structures in the Universe, making them a unique laboratory to probe cosmological physics.

I first introduce the Sunyaev-Zel’dovich (SZ) effect as a powerful method for finding galaxy clusters, and recount the current progress/problems in understanding cluster SZ properties. As an example, I will then discuss how study of clusters can teach us about the (potential) non-gaussianity of the cosmological initial conditions.