Summary: Raman spectroscopy analyzes non-elastically scattered light from chemical bonds (Fig. 1). Photons from a laser source are scattered by interaction with molecular bond vibrations and either deposit energy into a particular bond or receive additional energy from an already excited bond vibration. Different molecular bonds have different vibrational frequencies and lead to specific peaks in the Raman spectrum. For instance, a C-C bond can be easily distinguished from a C=C bond, allowing us to distinguish saturated from unsaturated lipids. All biomacromolecules, including DNA, RNA, proteins, and lipids, have characteristic Raman modes, which enable the nondestructive determination of their chemical composition and structure. Raman spectroscopy provides complementary information to mass spectrometry or magnetic resonance imaging (MRI) without destroying cells in the process of the analysis, with high spatial resolution akin to confocal optical microscopy, and without the need for contrast agents - enabling live imaging at the cellular level. In our LTRS system we have further increased the sensitivity of Raman spectroscopy at the cellular and sub cellular level by combining laser trapping and Raman spectroscopy. Here, a tightly focused laser beam, such as the one obtained by sending the beam through a high resolution immersion oil microscope objective, forms an optical laser trap which captures cells or lipoproteins and confines them to the laser focus until the laser is turned off or another particle collides with the one captured. Modified from: Chan JW, et.al. Anal. Chem. 2005 Sep 15;77(18):5870-76.