Folate-functionalized quantum dots, gold/silver nanoparticles, and magnetic quantum dots have been synthesized and used as fluorescence, dark-field, and dual-imaging probes for the detection of cancer cells and tissues. A very efficient and generalized folate-functionalization method has been developed for various amine-terminated nanoparticles. The advantages of the presented approach are that it can be used to synthesize a wide range of folate-functionalized nanoparticles and the number of folate molecules per nanoparticle can be controlled easily to tune their interaction with folate receptors present at the cell surface. These folate-functionalized nanoparticles have been used as cellular and tissue-imaging bioprobes. Results show that folate-functionalized nanoparticles act as efficient and selective imaging probes in targeting cancer cells and tissues and labeled cells/tissues can be detected by using different imaging modalities.