This overview deals with the current and future scopes of ionic liquid studies. The hot topics (1) fundamental understanding of ionic liquid properties, (2) utilization of ionic liquids as new materials, and (3) realization of green chemistry by using ionic liquids as new solvents, are individually presented in relation to our own research. The characteristics of ionic liquids deeply owe to the facts that they keep liquid states at ambient temperatures, in spite of the large ion-ion interaction, and dissociate into ions in the absence of solvents. The role and position of ionic liquids as “designers solvent” should be established based on the fundamental understanding between the ionic structure and the properties.