This thesis develops a novel photopatterning strategy for biomimetic scaffolds that enables spatial and biochemical control of engineered cellular architectures, such as the microvasculature. Intricate tools that allow for the three dimensional (3D) manipulation of biomaterial microenvironments will be critical for organizing cellular behavior, directing tissue formation, and ultimately, developing functional therapeutics to treat patients with critical organ failure. Poly(ethylene glycol) (PEG) based hydrogels, which without modification naturally resist protein adsorption and cellular adhesion, were utilized in combination with a two-photon laser patterning approach to covalently immobilize specific biomolecules in custom-designed, three-dimensional (3D) micropatterns. This technique, known as two-photon laser scanning lithography (TP-LSL), was shown in this thesis to possess the capability to micropattern multiple different biomolecules at modular concentrations into a single hydrogel microenvironment over a broad range of size scales with high 3D resolution. 3D cellular adhesion and migration were then explored in detail using time-lapse confocal microscopy to follow cells as they migrated along micropatterned tracks of various 3D size and composition. Further, in a valuable modification of TP-LSL, images from the endogenous microenvironment were converted into instructions to precisely direct the laser patterning of biomolecules within PEG-based hydrogels. 3D images of endogenous microvasculature from various tissues were directly converted into 3D biomolecule patterns within the hydrogel scaffold with precise pattern fidelity. While tissue engineers have previously demonstrated the formation of vessels through the encapsulation of endothelial cells and pericyte precursor cells within PEG-based hydrogels, the vessel structure had been random, uncoordinated, and therefore, ultimately non-functional. This thesis has utilized image guided TP-LSL to pattern biomolecules into a 3D structure that directs the organization of vessels to mimic that of the endogenous tissue vasculature. TP-LSL now stands as a valuable tool to control the microstructure of engineered cellular architectures, thereby providing a critical step in the development of cellularized scaffolds into functional tissues. Ultimately, this thesis develops new technologies that advance the field of regenerative medicine towards the goal of engineering viable organs to therapeutically treat the 18 patients who die every day waiting on the organ transplant list.