This issue of ECS Transactions on Semiconductor Wafer Bonding will cover the state-of-the-art R&D results of the last 2 years in the field of semiconductor wafer bonding technology. Wafer Bonding is an Enabling Technology that can be used to create novel composite materials systems and devices that would otherwise be unattainable. Wafer Bonding today is rapidly expanding into new applications in such diverse fields as photonics, sensors, MEMS. X-ray optics, non-electronic microstructures, high performance CMOS platforms for high end servers, Si-Ge, strained SOI, Germanium-on-Insulator (GeOI) and Nanotechnologies.