Researchers developed molecular aging clocks to measure the biological versus chronological age of individual neuron types in C. elegans worms, discovering that certain neural populations maintain youthful function despite organism-wide aging. The study found that motor neurons and sensory neurons age at dramatically different rates, with some sensory cells showing minimal biological aging even in chronologically old animals. This cellular-level precision in aging measurement represents a significant methodological advance over tissue-wide or organism-wide aging assessments. The findings have profound implications for understanding selective vulnerability in neurodegenerative diseases like Alzheimer's and Parkinson's, where specific neuron types deteriorate while others remain intact. Previous aging research has largely treated the brain as a homogeneous organ, but this work reveals that neuronal aging is highly heterogeneous at the cellular level. The identification of naturally resilient neuron types could guide therapeutic strategies aimed at conferring similar protection to vulnerable populations. While conducted in a simple model organism, the approach establishes a framework for mapping neuronal aging patterns in mammalian brains, potentially revealing why some individuals maintain cognitive sharpness despite advanced age while others experience rapid decline.