Cosmic dust are extraterrestorial particles less than 1 mm meter, coming from a wide range of possible parental sources such as Comets, Asteroids, Moon, Mars and an interstellar stream of dust. They would provide valuable evidence on the origin of solar system that cannot be derived from meteorites. In the present paper, collection sites and methods of cosmic dust are introduced including those from and by which the first Japanese cosmic-dust collection was recovered. Then, origin and formation process of cosmic dust is discussed based on the mineralogical and compositional data taken by the recently innovated techniques for the analyses of very small particles.