"... in the closing line of Darwin's ', he remarked on 'endless forms most beautiful', and he was referring to the incredible diversity of s ... much of his research and thinking had to with trying to understand: How do we get this diversity of s? And, there's been a great deal of progress in this regard, largely from the work of s, s, and s working together to try to understand what are molecular mechanistic underpinnings of the diversification of animal body plans. ... Animals are united by their shared ancestry. They all share a common ancestor … And, in fact, we know relatively little about the nature of that organism."