Luminescent inorganic nanocrystals (Q-dots). The emission wavelength is a function of the crystal size - crystals of the same chemistry can have the emission maxima in a wide range. CdTe hydrophilic Q-dots are coated with -COOH groups and can be easily used for labeling purposes for chemical and biological applications. CdSe/ZnS and ZnCdSe/ZnS (core/shell type) Q-dots are hydrophobic and are soluble in most non-polar organic solvents