A new study gives insight into how how stem cells differentiate. New findings show that embryonic stem cells must be fully able to compact the chromatin inside of them to differentiate into the specific cell types that give rise to the various tissues and structures within the body. Chromatin, composed of histone proteins and DNA, packages DNA so that it fits inside a cell. Stem cells that lacked three subtypes of the histone H1 had impaired differentiation under multiple scenarios.“By showing that H1 plays a part in controlling genes that direct embryonic stem cell differentiation, the study expands our understanding of H1’s function and offers valuable new insights into the cellular processes that induce stem cells to change into specific cell types,” Anthony Carter, who oversees epigenetics grants at the National Institutes of Health’s National Institute of General Medical Sciences, which supported the work.