To detect individual chemical substances in a biological tissue and to visualize their distribution by visual light microscopy usually it is necessary to stain these substances using molecular colorants.
In contrast the IR-spectroscopic analysis does not require any staining of the molecular classes of interest. In fact they can be identified by the vibrational modes of their characteristic functional groups. As the signal intensities are proportional to the concentrations of the absorbing molecules the IR-measurement also shows the relative distribution of several molecular classes inside the analyzed area.
Animal and plant tissues are usually measured in transmission. For the FT-IR-microanalysis of biomedical materials like stents, implants or protheses also the other available measurement modes are applied.