Albert Einstein developed the general theory of relativity 100 years ago as an answer to fundamental problems of contemporary physics. Yet the theory remained a marginal phenomenon of physics, especially in comparison to quantum theory, until the second half of the twentieth century. That's when the renaissance in general relativity combined with the rise of relativistic astrophysics, turning general relativity into a key instrument in astrophysics. This talk will trace the genesis of general relativity, look at Einstein's research and the work of many other scientists who contributed to the theory, and show how general relativity eventually became not only a highly active field of research but one of the principal challenges to the conceptual unification of physics.