The key principles and modern approaches to targeted modification of semiconductor colloidal nanopar-ticles, quantum dots, which exhibit unique photophysical properties and are a promising class of luminescent markers, are discussed. Attention is given to the preparation of their bioconjugates with nucleic acids, promising tools for biological microchips and resonance energy transfer sensors. The bibliography includes 80 references. © 2011 Russian Academy of Sciences and Turpion Ltd.