In a biorxiv paper posted two days before Amon’s passing, researchers in her group, with collaborators in the Lees and Yilmaz labs, illuminate the relationship between stem cell size and function, and tissue aging. Despite great variability in cell size and shape between tissues, stem cells are invariably small. The Amon lab’s studies present evidence that small size is critical for hematopoietic stem cell function. Analyses of these cells also showed that they get progressively bigger with organismal aging, and that the larger stem cells are less functional. These findings suggest that large size causes stem cell function to decline during aging. This work was partly supported by the MIT Stem Cell Initiative.