Brain is arguably the most complex organ in biology. It shows a heterogeneous structure, in which different areas are responsible for different functions. New non-invasive techniques to monitor the structure and/or composition of the brain can help to understand this organ. In this paper, we show successful random lasing from a mouse brain tissue impregnated with a dye laser and demonstrate that it can be used to detect changes in structure and composition. We systematically observe that the lowest random lasing threshold and highest intensity are recorded in the corpus callosum anatomical region of the brain. This area is formed by a large number of axon fibers coated by myelin, which is a lipid rich substance. Both the fiber structure and the lipid rich composition contribute to increase the scattering strength, which improves random lasing. A thorough photoluminescence characterization of the tissues as a function of the staining concentrations is also included in the study
