Leonid Khriachtchev graduated from Leningrad State University, Russia, in 1981. He completed his PhD study in Quantum Electronics in 1986 and became a senior scientist and a group leader in 1988 at the Institute of Physics of the same university. That time, his research mainly dealt with resonant light pressure and optical pumping of the ground state of atoms in the gas phase and laser technique. In 1994, he joined the University of Helsinki, Finland, and he is currently with the Laboratory of Physical Chemistry of this university. His scientific interests include experimental optical and laser spectroscopy of matrix-isolated species and nanoscale materials. He has contributed to the construction of new chemical bonds, including the first argon chemical compound, HArF, and light-induced conformational changes at low temperatures. Optical and structural studies of silicon nanocrystals have been another important part of this research activity. He is the editor of the book Silicon Nanophotonics: Basic Principles, Present Status, and Perspectives, (World Scientific Publishing, 2008). He is the author of about 180 refereed articles.