Radiocesium-bearing microparticles (CsMPs) were emitted from the damaged reactors to the environment during the Fukushima Daiichi Nuclear Power Plant accident. This review summarizes current knowledge with respect to the inner structures and physicochemical characteristics of CsMPs. CsMPs are composed of micron-sized spherical silicate glass with Na, Cl, K, Fe, Zn, Rb, Sn, and Cs as major constituent elements. Besides, CsMPs frequently contain nanocrystals such as Cr-rich oxides and chalcogenides. Thermal and dissolution properties of CsMPs have also been elucidated recently. Radiocesium is released from CsMPs to the atmosphere if they were heated at a high temperature. The aqueous dissolution rate of CsMPs depends on pH and dissolved species in solutions, which is similar to that of silica glass. Estimation of the amount and spatial distribution of CsMPs in the environment is also progressing. These findings will lead to the comprehensive elucidation of the dynamics of CsMPs in the environment.