Engineers have discovered that some brain cells age more rapidly than others, and they are disproportionately abundant in individuals afflicted with Alzheimer's disease. Additionally, researchers observed male-female-specific differences in the aging process of certain brain cells, with the female cortex exhibiting a higher ratio of 'old' oligodendrocytes to 'old' neurons compared to the male cortex. The discoveries were made possible by a new technique called MUSIC (multinucleic acid interaction mapping in single cells), which allows researchers to peek inside individual brain cells and map out interactions between chromatin--which is the tightly coiled form of DNA -- and RNA.