Supercritical water is miscible with organic materials. Using this feature, the organically-modified metal-oxide nanoparticles can be synthesized. Organically-modified nanoparticles “organic-inorganic hybrid nanomaterials” can be dispersed in organic solvents at very high concentration. We aim to establish novel fundamental of material/process design for such nanomaterials, which behave like “molecules”. In addition, using nanocatalyst synthesized by supercritical water, we are developing innovative chemical processes for utilization of low-temperature waste heat.