The Youth Astronomy Network (YouthAstroNet for short) is a national, online community of youth, educators, and scientists that aims to help youth gain confidence and identity as someone who can do science through personal participation in authentic inquiry, supported by unique access to the resources of the Center for Astrophysics | Harvard & Smithsonian. Young people in every neighborhood, urban or rural, have questions about the universe. But many youth, particularly those in underserved communities, have few opportunities to engage their curiosity through rich, multidisciplinary, technology-enabled science learning experiences. YouthAstroNet helps middle school-aged students leverage their talents and creativity through astronomy programming as they build skills, and learn how these skills transfer to many exciting STEM disciplines. Our research has shown that science identity—the feeling of “being a science person”—is an important ingredient in motivating young people to persist in STEM learning. The Essential Elements of the YouthAstroNet experience—pursuing questions of personal interest with real telescopes; making sense of astronomical images through data analysis tools and hands-on activities; and youth-created capstone projects to communicate learning to peers, family and community—have been shown to produce gains in participants’ science identity and STEM career interest. The project is now researching conditions that support sustainable scale up of the program..