The ability to three-dimensionally pattern semiconducting materials could provide a transformative approach to creating active electronic devices without the need for conventional microfabrication facilities. This could enable the generation of active electronics on-the-fly, using only source inks and a portable 3D printer. Developing the ability to 3D print various classes of materials possessing distinct properties will enable the freeform generation of active electronics in unique functional, interwoven architectures. Yet, achieving seamless integration of these diverse materials via 3D printing is a substantial challenge which requires overcoming discrepancies in material properties in addition to ensuring that the materials are compatible with the 3D printing process. We present a strategy for three-dimensionally integrating diverse classes of materials using a custom-built 3D printer to create fully 3D printed devices built around active electronics. These results represent a series of critical steps toward the 3D printing of high performance, active electronic materials and devices.