Question #1: Where go the events?

I.e. UI events. If MVVM prescribes a no-codebehind vision, where are the UI events (e.g. on-change states of datagrids, etc.) handled? Declarative triggers? MVP appears to make allowance for the events (commands are handled well by MVVM). Can we live without UI events? More specifically, can we do without handling them in the codebehind. The workaround I suppose is to use custom attached behaviors or EventSetters.