Hair greying is thought to be an irreversible event related to life stress, but the process has never been extensively studied. For the first time, researchers at Columbia University use novel techniques with hair imaging and a daily diary to demonstrate that hair greying is not only associated with stressful life events, but that the process is reversible and correlated with metabolic changes in mitochondria. Better understanding this process may give us more information on how our bodies biologically respond to psychological stressors and opens new roads to potentially reversing hair greying. Rosenberg et al. Quantitative mapping of human hair greying and reversal in relation to life stress. eLife, June 2021. DOI: 10.7554/eLife.67437 The information presented here is not medical advice. Consult your physician on any questions regarding your personal health.