Semiconductor nanocrystals composed by few hundred to a few thousand atoms also known as quantum dots have received substantial attention due to their size tunable narrow-emission spectra and several other advantages over organic molecules as fluorescent labels for biological applications, including resistence to photodegradation, improved brightness and only one laser excitation that enable the monitoring of several processes simultaneously. In this work we have synthesized and characterized thiol-capped CdTe and bioconjugated them to macrophages. We have mapped the fluorescence intensity along the macrophage's body in our set up consisting of an optical tweezer plus a non-linear micro-spectroscopy system to perform scanning microscopy and observe spectra using two photon excited luminescence.5704 193199Borchert, H., Talapin, D.V., McGinley, C., High resolution photoemission study of CdSe and CdSe/ZnS coreshell nanocrystals (2003) J. Chem. Phys., 271, pp. 1800-1807Alivisatos, A.P., Semiconductor clusters, nanocrystals, and quantum dots (1996) Science, 271, pp. 933-937Nowak, C., Döllefeld, H., Eychmüller, A., Innershell absorption spectroscopy on CdS: Free clusters and nanocrystals (2001) J. Chem. Phys., 114, pp. 489-494Bruchez Jr., M., Moronne, M., Gin, P., Weiss, S., Alivisatos, A.P., Semiconductor nanocrystals as fluorescent biological labels (1998) Science, 281, pp. 2013-2016Chan, W.C.W., Nie, S., Quantum dots for ultrasensitive biological detection (1998) Science, 281, pp. 2016-2018Ballou, B., Lagerholm, B.C., Ernst, L.A., Bruchez, M.P., Waggoner, A.S., Noninvasive imaging of quantum dots in mice. Bioconjug (2004) Chem., 15, pp. 79-86Gao, X., Nie, S., Molecular profiling of single cells and tissue specimens with quantum dots (2003) Trends Biotechnol., 21, pp. 371-373Äkerman, M.E., Chan, W.C.W., Laakkonen, P., Bhatia, S.N., Ruoslahti, E., Nanocrystal targeting in vivo (2002) Appl. Biol. Sci., 99, pp. 12617-12621Chan, W.C.W., Maxwell, D.J., Gao, X., Bailey, R.E., Han, M., Shuming, N., Luminescent quantum dots for multiplexed biological detection and imaging (2002) Curr. Op. Bioteh., 13, pp. 40-46Mattheakis, L.C., Dias, J.M., Choi, Y., Gong, J., Bruchez, M.P., Liu, J., Wang, E., Optical coding of mammalian cells using semiconductor quantum dot (2004) Anal Biochem., 327, pp. 200-208Konig, K., Laser tweezers and multiphoton microscopes in life sciences (2000) Hyst. and Cell Biol., 114, pp. 79-91Goodman, M.M., Knapp Jr., F.F., (1983) Organometallics, 2, pp. 1106-1108Gaponik, N., Talapin, D.V., Rogach, A.L., Hoppe, K., Shevchenko, E.V., Kornowski, A., Eychmüller, A., Weller, H., Thiol-capping of cdte nanocrystals: An alternative to organometallic synthetic routes (2002) J. Phys. Chem. B, 106, pp. 7177-7718Rosenthal, S.J., Tomlinson, I., Adkins, E.M., Schroeter, S., Adams, S., Swafford, L., McBride, J., Blakely, R., Targeting cell surface receptors with ligand-conjugated nanocrystals (2002) J. Am. Chem. Soc., 124, pp. 4586-4594