Carl R. Woese, of Urbana, Illinois, was the man who invented molecular phylogenetics. Although famous to researchers in molecular evolution and microbiology—revered by many, suspect to some—he remains almost entirely unknown to the general public. Even among organismic biologists, ecologists, and evolutionary biologists who study flora and fauna, the name Woese draws a blank. He is arguably, as I’ve often said to such people, “the most important biologist of the 20th century that you’ve never heard of.” It was Woese who discovered a third major domain of creatures, the Archaea. It was Woese who hit upon the notion of using 16S rRNA, at the core of the translation apparatus, as a Rosetta Stone molecule for discerning phylogeny. And it was Woese’s work that led forward to recognition of the scope and the significance of horizontal gene transfer (HGT), as an evolutionary factor, throughout life’s history and across all domains. Because of Carl Woese, we now comprehend that the “tree of life” is not shaped like a tree. Given those contributions, it’s peculiar and somewhat unfortunate that he is so little known. But it’s fortunate for me, because I’ve just written a book about him—with the help of insights and memories generously shared by many of his colleagues and friends, including George Fox, Norman Pace, Ralph Wolfe, Linda Bonen, Ford Doolittle, Harry Noller, and Larry Gold. Drawing on the work, and the memories, I will talk about Carl Woese as a scientist and a man.