System integration is clearly a driving force for innovation in packaging. The need for miniaturization has led to new architectures that combine disparate technologies and materials. Today several different approaches have been developed. These include technologies like system in package. In this way, a new concept for heterogeneous integration is currently being developed at CEA-LETI and is called system on wafer (SoW). This concept is based on a chip to wafer approach. Every component is achieved by using wafer-level technologies, and the final system is performed by single component mounting on a silicon substrate. The main strength of this approach is to use silicon as a substrate for components and for basic support. To perform the SoW, a generic technological toolbox is needed. This includes every standard packaging technology such as flip chip, signal rerouting, and passive component integration as well as new advanced technologies such as microelectromechanical systems packaging, advanced interconnections, energy source integration, integrated cooling, or silicon through vias. In this paper, the SoW concept will be presented and the generic toolbox for SoW achievement will be described.