We couldn't figure out how they just keep growing without food until one night, I saw a baby spider clinging onto its mom's belly,” Zhanqi Chen at Chinese Academy of Science says. “I had this radical idea that maybe spider moms feed their babies with something they produced.” So Chen and his colleagues put mother spiders under the microscope and gently squeezed their abdomens. A few droplets of a creamy white fluid came out, something that looked very similar to human or other mammalian milk.