Flow fluctuations and long-range correlations: elliptic flow and beyond

This paper consists of a brief overview of current understanding of collective behavior in relativistic heavy-ion collisions. In particular, recent progress in understanding the implications of event-by-event fluctuations has solved important puzzles in existing data-the 'ridge' and 'shoulder' phenomena of long-range two-particle correlations- and has created an exciting opportunity to tightly constrain theoretical models with many new observables.