Marshall Henry Klaus was a scientist and pediatrician who studied maternal-infant bonding in the twentieth century in the United States. Maternal-infant bonding is the psychological and chemical attachment between mother and infant. Klaus cofounded DONA International, an organization that trains birthing aides, called doulas, to provide physical and emotional support to laboring mothers. He also studied the differences between the layouts and quality of care provided in nurseries and birthing centers in different countries and compared them to those found in the United States. Klaus’s study influenced national and international initiatives to create hospital policies focused on promoting early bonding between mother and infant. Klaus catalyzed the advent of doulas and international policies that emphasized interaction between new mothers and their infants.