Light is an environmental factor that regulates many growth characters of in vitro cultures, trough the leading of photomorphogenesis processes. Photoperiod and light intensity have been rather extensively studied in the past, but the effects of light quality on the development and growth of in vitro cultures are still not well known, in particular when woody species are cultured. In this review, knowledge acquired up to day on the role of light quality on in vitro cultures is presented in the view of pointing out the scientific aspects, and the possible application, of specific light qualities that could improve the in vitro culture efficiency. After an outline on the role of the photoreceptors and on physiological features of micropropagation systems, the effects of different light spectra on shoot multiplication, elongation and rooting, and on leaf development and functionality are reported. Technical aspects of lamp types conclude the work.