Tetsuo Irifune has been working on the materials in Earth’s deep interior, based on ultrahigh-pressure experiments and in situ synchrotron X-ray observations. He also invented ultrahard nano-polycrystalline diamond (= NPD or Hime diamond) using ultrahigh-pressure synthesis technique and has been involved in applications of NPD to various research fields, in collaboration with domestic/overseas research groups. He served as the President of International Association for the Advancement of High Pressure Science and Technology, and as the Director of the global COE program “Advanced Experimental and Theoretical Research Institute for Deep Earth Mineralogy”. He received Medal with Purple Ribbon, A.V. Humboldt Award, R.W. Bunsen Medal, P.W. Bridgman Medal, etc., and selected as Fellows of American Geophysical Union (AGU) and Japan Geoscience Union (JpGU).