For much of the 20th century, doll manufacturers have worked to produce dolls that look and move like infants. In the 1920s, doll designer Grace Storrey Putnam presented the Bye-Lo baby, an incredibly popular doll crafted to look like a three-day-old newborn. In the 1930s, one doll maker developed the Dy-Dee doll, the first of the drink-and-wet dolls. Betsy Wetsy, Tiny Tears, and others followed. With the introduction of dolls made of plastic and vinyl in the 1950s, doll manufacturers perfected baby dolls with a variety of functions including eating, crawling, walking, talking, playing peek-a-boo, and even responding to a child's voice. Baby dolls of all kinds serve a special kind of nurturing play in the pretend worlds of young children.