This memoir describes the professional life and times of Thomas D. Brock, with an emphasis on those aspects of his career relating to research in microbial ecology, and how this work led to field research in Yellowstone. The first discovery of extremely thermophilic bacteria is described, followed by a discussion of some of the consequences of this discovery for biotechnology and microbiology. Also covered briefly in this memoir are Brock's activities in textbook writing, publishing, computers, and the history of science.