Part I Background -- 1. Vision of Pervasive Backscatter -- 2. Understanding State-of-the-art Ambient Backscatter -- Part II Backscatter Communication with Ambient Excitations -- 3. Spatial Stream Backscatter with MultiplexingWi-Fi -- 4. Single-SymbolWi-Fi Backscatter with Uncontrolled Ambient Signals -- 5. Symbol and Sub-symbolWi-Fi Backscatter for 802.11b -- 6. Content-Agnostic Backscatter with ambient OFDM signals -- Part III Towards Backscatter Networks at Scale -- 7. Multi-hopWi-Fi Backscatter -- 8. Multi-hop Backscatter Sensor Mesh -- 9. Multiprotocol BackscatterWith Commodity Radios -- Part IV Innovative Backscatter-Enabled Applications -- 10. Microphone Array Backscatter -- 11. Apollo: Battery-free wearable sweat monitoring system -- Part V Future Directions -- 12. Chapter Heading.