Fluctuations, collectivity and correlations in high-energy nuclear collisions
I present an overview of recent theoretical results on the azimuthal anisotropy of particle production in heavy ion and light-heavy ion collisions. I discuss the role of viscous fluid dynamics in describing the experimentally observed anisotropies and stress the importance of the initial state and its fluctuations. I will also discuss the role of initial state correlations in the color glass that are often neglected.