Based on characteristic vibrational spectra of endogenous molecules, many important structural components of tissue such as lipids (CH2-vibration, red), proteins (CH3-vibration, green), and water (OH-vibration, blue) can be imaged. The images show a sebaceous gland wrapping around a hair in the viable epidermis of mouse skin. (left) CH2-image in red shows the lipid-rich gland cells with sub-cellular resolution. Nuclei appear as dark circles due to the lack of lipids. (center) CH3-image in green shows residual lipid signal but also new protein-rich structures such as a hair in the center of the image, collagen fibers surrounding the gland and red blood cells in the top left. It can be seen that hair (green solid center) is surrounded by lipid-rich sebum (red circle). (right) OH-image due to water in blue shows inverse image contrast from the sebaceous gland because the lipid rich cells exclude water. Recent developments have allowed the acquisition of SRS images in reflection mode and at video-rate imaging speed in living mice and humans. Scale: 20μm.