"The assignment we were given for this article was to describe the impact of Einstein's work on 20th-century physics. This formulation of our task is somewhat problematic given that a sizeable fraction of 20th-century physics is Einstein's work and most of the rest is more or less directly connected to it. Hence Einstein's impact definitely cannot be treated perturbatively. In fact, it would have been much easier to write about those developments of 20th-century physics that were not connected to the work of Einstein. But who would want to read or write that?"