Fumio Inagaki is a geomicrobiologist, principal senior scientist, and director of the Mantle Drilling Promotion Office (MDP), Institute for Marine-Earth Exploration and Engineering (MarE3), Japan Agency for Marine-Earth Science and Technology (JAMSTEC). He obtained his Ph.D. at the Kyushu University, Japan (2000), Alexander von Humboldt Research Fellow at the Max Planck Institute for Marine Microbiology in Bremen, Germany (2005-2006), and was the deputy director of Kochi Institute for Core Sample Research and Research and Development Center for Ocean Drilling Science (ODS), JAMSTEC. His research interests are geomicrobiology and biogeochemistry of the ocean, with a special focus on the deep subseafloor biosphere. He uses scientific ocean drilling and the state-of-the-art transdisciplinary approaches to explore the limits of deep microbial life, ecosystem functionality in biogeochemical carbon cycles, co-evolution of life and Earth, and planetary habitability on Earth and beyond. In his early scientific career, he first isolated two novel mesophilic chemolithoautotrophic epsilon-proteobacteria (Sulfrimonas and Sulfurovum), the most abundant, ecologically significant sulfur and/or hydrogen-metabolizing bacteria globally distributed at cold seeps and deep-sea hydrothermal environments. Today, he has participated in 28 scientific research cruises, in which he served as (co-)chief scientist for 15 expeditions, including 3 co-chief expeditions of scientific ocean drilling (IODP Expeditions 329, 337, and 370). With his international leadership, numerous students, scientists, technicians, and ship-operators have been integrated into the challenging missions to explore the biosphere frontiers deep beneath the ocean. In 2012, using the Japanese riser-drilling research vessel Chikyu, his international team extended the world depth record of previous scientific ocean drilling down to ~2.5 km below the ocean floor. It showed evidence for the occurrence of deep subseafloor microbial life and their activity in ~20-million-year-old coal and shale beds. His current study includes the global abundance and distribution of three subseafloor life domains (Archaea, Bacteria, and Eukarya), adaptive evolution, and long-term survival strategy of subseafloor life, geosphere-biosphere interactions in plate subduction zones, and planetary habitability through scientific ocean drilling down to the upper mantle. Based on his knowledge and experience in Geomicrobiology, his research also includes applied science for developing sustainable carbon and energy systems—so-called Geobiotechnology. He published 200 peer-reviewed international articles and book chapters and more than 60 Japanese articles with >200 media coverages. He was a Deep Life steering committee member of the Deep Carbon Observatory (DCO) funded by the Alfred P. Sloan Foundation (2013-2019), a Senior Editor of The ISME Journal (2017-2019), the first awardee of the American Geophysical Union (AGU) Asahiko Taira Scientific Ocean Drilling Research Prize (Taira Prize) in 2015, the Cozzarelli Prize of National Academy of Science in 2017 (Category IV), the Copernicus Medal in 2019 at the European Geophysical Union (EGU), and Geochemistry Fellow of Geochemical Society (GS) and European Association of Geochemistry (EAG) in 2021. He is Associate Editor of Science Advances, AAAS (since 2019), and Advisory Board member of Earth 4D: Subsurface Science & Exploration, CIFAR, Canada (since 2019). His international academic services include a steering committee member of the International Society of Subsurface Microbiology (ISSM, since 2017) and the Program Committee Co-chair of the Japanese Geoscience Union (JpGU)-AGU Joint Meeting 2020. He is Guest Professor at Waseda University and Kochi University, Japan （2020.4-present) and is Professor at Tohoku University, Japan (2021.3-present).