Avoid shocking your hematopoietic stem cells to keep them young and growing.

Expanding hematopoietic stem cells (HSCs) ex vivo has historically been a very challenging process. In this issue of Cell Stem Cell, Kruta et al. (2021) identify heat shock factor 1 (Hsf1) as a new target to maintain HSC fitness and protein homeostasis, not only in culture conditions but also upon aging.