124 Background The remote identification of the chemical composition of atmospheric aerosols and clouds is useful for the study of acid rain and for developing global climate models. In addition, the remote sensing for atmospheric microparticles such as saltwater aerosols is desirable to solve the corrosion problem of buildings, such as electrical power plants, by sea salts. However, a technology to remotely measure the constituents of microparticles in air at a distance of more than several tens meters is not the level of practical use. Laser-induced breakdown spectroscopy (LIBS)*1 is attractive for the real time remote sensing of the constituents of microparticles in air. A bundle of filaments, which propagate for long distances with a focused condition, can be generated using a recently developed ultrashort-pulse high-intensity laser. This unique laser beam is expected to drastically improve the sensitivity of LIBS measurements of microparticles in air because a large number of microparticles can be ionized along filaments in air for a long distance, which can realize lidar measurements.