Are makerspaces--where children can create gas-powered Roman chariots, singing greeting cards, or playdough circuit boards--just the site for a slightly wacky explosion of inventiveness? Or can these maker activities be channeled to support deep STEM learning? Bronwyn Bevan, director of the Exploratorium Institute for Research and Learning in San Francisco, has been developing maker activities for years. In this article, she describes how such activities, also known as tinkering, can help students develop productive science learning identities--that is, to be interested in science, to feel capable of doing science, and to want to do science. As they build electrical circuits that will set motorized fans whirring or create objects that float in wind tunnels, students engage in prediction, design, testing, revising, and retesting. Bevan recommends that schools introduce a maker program in an afterschool or family night context, and then expand the maker approach to classroom activities.