There are many interesting science targets in the pressure region above the Earth's center pressure. The double-stage diamond anvil cell (ds-DAC) is considered as one of the key techniques of the static compression experiment for generating such extremely high-pressure conditions. Here I review about the basic of ds-DAC technique, micro-paired ds-DAC (including failure story), conical support type ds-DAC, the material of micro-anvil, the example of the implication for the X-ray absorption spectroscopy (XAS) measurement, and the detail of the fabrication method of micro-anvils using focused ion beam (FIB) system and the preparation of ds-DAC experiments.

In this article, I review our vibrational spectroscopic studies of the clathrate hydrates containing methane and ethane as guest molecules at low temperatures and high pressures. Our results will contribute to a better understanding of the rotational dynamics of the guest methane molecule under high pressure, the cage occupancies in the high-pressure phases of methane hydrate, and the structures after pressure-induced amorphization.

I report a simple shock event approach inspired by the Allende meteorite to produce sophisticated carbon nanomaterials. It is demonstrated that unique carbon nanostructures, including carbon nanotubes, carbon onions, and new carbon nanorings are synthesized by super-high-energy ball-milling of steel balls. I propose that such carbon nanostructures exhibit an ultraviolet (UV) absorption feature at 220 nm that I suggest accounts for the UV interstellar extinction at 217.5 nm. Then, I report that 0.5FeTiO₃·0.5Fe₂O₃ solid solution compressed by collision synthesis with super-high-energy ball milling shows a decrease in molar volume of approximately 1.8 %. Consequently, the sample shows a new ferromagnetism with high Curie temperature. I propose that the compressed ilmenite–hematite solid solution is a potential candidate source of planetary magnetic anomalies.

We developed a method to determine the absolute pressure effect on thermocouple electromotive force, based on a single wire method using Kawai-type multi-anvil apparatus. In this method, pressure conditions along the wires were evaluated based on in situ X-ray diffraction using synchrotron radiation. The pressure effect of the Seebeck coefficients for materials of type K, D, and R thermocouples were determined up to 16 GPa and 1173 K. The difference between the nominal and real temperatures was large especially for type R (−75 K at 13 GPa and 873 K). Recent technical developments enabled to conduct similar measurements above 20 GPa. The accurate evaluation of error in thermocouple nominal temperature would be highly important in many research fields including geophysics.

High-pressure food processing technique has originated in Japan, and its technique is used all over the world. A few years ago, the author suddenly encountered the "high-pressure", and then started to produce the new high pressure-processed food and its industrial application. Our final goal is to put the ultimate food product with many added values out into the world, whose shelf life is significantly extended by advanced control of bacteriostatic condition. On the way, we faced many troubles but finally succeeded to produce "high-pressure bento", which has many added values nobody has ever seen and is to be patented. Here, we briefly introduce our initiatives and some products with manufacturing procedure.

High-pressure synthesis is a useful method for exploring and synthesizing novel compounds. In this article, transition-metal nitrides and intermetallic compounds of transition-metals and metalloids synthesized under high pressure by utilizing both large-volume press (LVP) and diamond anvil cell (DAC) are reviewed. Further advances in materials science are expected by combining high-pressure synthesis and new reaction process. Control of physical properties by synthetic pressure is achieved in addition to novel compound synthesis.