Specifically, we identified 5′‐tsRNAs from sorted stem and differentiating cell populations from murine skin [CD34+α6+ stem vs. CD34−α6+ non‐stem cells (Fig EV1F); human mammary epithelial cells (HMECs) at different stages of oncogenic transformation as they gain stemness (Fig EV1G and G′) 19, 20; and CD44+CD24− (stem) vs. CD24+ (non‐stem) cells in two breast cancer cell lines, namely MDA‐MB‐231 (Fig EV1H) and HS578T (Fig EV1I)]. Here, CD34 is linked to breast cancer.