All of life on earth is divided into three major domains- the Bacteria, Archaea and Eukarya. This is the universal phylogenetic tree based on a gene that we all have, the ribosomal RNA. We (humans) are located in the crown group of animals, but the majority of diversity on this planet is in the microbial (bacterial and archaeal) world. Those lines highlighted in red lead to organisms that are heat-loving, the focus of much of our work at deep-sea hydrothermal vents. Image adapted from Woese et al. 1990.