App Inventor, a free and revolutionary online program from MIT, lets you build your own mobile apps. With the help of this companion guide chock-full of colourful graphics and easy-to-follow instructions, readers can learn how to create six different apps, including a working piano, a maze game, and even their own chat app – then use what they’ve learned to build apps of their own imagination. User-friendly code blocks that snap together allow even beginners to quickly create working apps. Readers will also learn about young inventors, such as the girls from Moldova, whose app lets people in their community check the water quality of local wells. Or Chimayi in Bangalore whose app monitors pollution levels in the city. With this inspiring guide, curious young dreamers can become real inventors with real-world impact.