When the thermometer approaches 30 degrees, you can easily create your own air conditioning. When friends come over to watch football, you can turn a smartphone into a projector. You can make a Wi-Fi extender if the internet doesn't reach the attic. Wouldn't that be nice? But how? It's simple: with physics! Philip Häusser explains how anyone can recreate these brilliant inventions. He particularly focuses on the physical principles behind the inventions and provides an informative and entertaining overview.