Space dust is a major astronomical factor, which affects most observations in UV, optical, infrared, submillimeter, etc. Most often it is an obstacle, preventing us from getting undistorted information on various astronomical objects. Dust in star-forming regions is different. It is not only an obstacle but also an important tracer of physical conditions in these regions, a catalyst for interstellar chemistry, and a progenitor for planetary systems. In order to clarify all these various roles, we need to know properties of space dust and how they may change on different stages of the star formation process.