Elizabeth Dexter "Betty" Hay (April 2, 1927 – August 20, 2007) was an American cell and developmental biologist. She was best known for her research in limb regeneration, the role of the extracellular matrix (ECM) in cell differentiation, and epithelial-mesenchymal transitions (EMT). Hay led many research teams in discovering new findings in these related fields, which led her to obtain several high honors and awards for her work. Hay primarily worked with amphibians during her years of limb regeneration work and then moved onto avian epithelia for research on the ECM and EMT. Hay was thrilled by the introduction of transmission electron microscopy (TEM) during her lifetime, which aided her in many of her findings throughout her career. Moreover, Hay was a huge advocate of women in science