Cells need blood vessels to transport nutrients, oxygen, and waste. The lack of vascularization within engineered tissues results in a loss of tissue viability and function, limiting the ultimate success of tissue engineering strategies. Thus, there is a tremendous need to understand how to efficiently grow blood vessels in vitro within the context of engineered tissues. As bioprinting and other microfabrication technologies improve in resolution, it has become increasingly possible to define the structure of tissues such as blood vessels by placing the cells in pre-defined positions. Additionally, endothelial cells have an intrinsic ability to self-organize into microvascular networks. My research combines these two ideas: laying down the general structure of the network by cell patterning and then allowing the cells to progress through the later stages of tissue morphogenesis to create a functional capillary network. My dissertation research proposes that we can control and enhance the intrinsic self-organization capabilities of pre-patterned endothelial cells by changing their microenvironment – the chemical, cellular, and physical cues that impinge upon the cells. By adjusting the microenvironment to promote certain cell behaviors involved in vasculogenesis, I was able to guide patterned endothelial cells to self-organize into pre-defined capillary-like vessels.