There is a large deficit of donor organs in transplant surgery. Moreover, autologous free tissue transfer in reconstructive surgery is imperfect due to invasive harvesting of tissue and the long duration and complexity of the operation. The biofabrication of organs is a promising strategy to diminish the shortage of donor organs and to resolve the shortcomings in free autologous tissue transfer. To biofabricate large organs, the integration of vasculature is essential. This comprises a microvascular network that overcomes the diffusion limits for oxygen and nutrients and macrovasculature that permits fast perfusion of the whole construct when connected to an in vitro or in vivo circulatory system. In this research project, a vascular model for organ engineering will be created that comprises both macro- and microvasculature. The macrovasculature will be 3D bioprinted with a novel vascular biomaterial. To form the microvascular network, angiogenesis from the macrovasculature towards vascularized microtissues will be stimulated using biomaterial modifications and saRNA technology. In contrast to the current state-of-the-art, this model will be suitable for direct connection to the host’s vasculature by surgical anastomosis, which will make the transplantation of large 3D bioprinted organs possible. Additionally, the biofabricated macrovasculature can be tested as a small diameter graft for bypass surgery.