We study basic phenomena in indirect excitons (IXs). IXs are bound pairs of spatially separated electrons and holes created in semiconductor structures. Due to their long lifetimes, IXs cool below the temperature of quantum degeneracy. This allows the realization and studying of cold bosons in semiconductors. IX parameters are controlled by structure design, voltage, and light and IX properties are measured by optical spectroscopy at temperatures from 50 mK in optical dilution refrigerator to room temperature. Phenomena studied by the group in IX systems include new states of matter, Bose-Einstein condensations and spontaneous coherence, mesoscopics of bosons, pattern formation, transport and localization, spin currents and spin textures, bosons in magnetic fields, and correlations.