App Inventor is an open-source tool that democratizes app creation for and by all. By combining visual LEGO-like blocks together on the screen, even users with no prior programming experience can use App Inventor to create their own mobile applications. Currently, App Inventor has over 1,000,000 users and is being taught by universities, schools, and community centers worldwide. In those initiatives, students not only acquire important technology skills such as computer programming, but also have the opportunity to apply computational thinking concepts to many fields including science, health, education, business, social action, entertainment, and the arts. Work on App Inventor was initiated in Google Research by Hal Abelson and is continuing at the MIT Media Lab as part of its Center for Mobile Learning, a collaboration with the MIT Computer Science and Artificial Intelligence Laboratory (CSAIL) and the Scheller Teacher Education Program (STEP).