The chapter discusses the current challenges and strategies in vascularization for tissue engineering. The primary challenge is the limited size of tissue constructs due to nutrient and oxygen diffusion limitations, which restrict the integration of these constructs in vivo. To address this, researchers have explored various approaches, including scaffold functionalization, cell-based techniques, bioreactor designs, microelectromechanical systems (MEMS), modular assembly, and in vivo systems. Each approach aims to improve oxygen and nutrient transport, enhance vascularization, and facilitate integration with host vasculature. Scaffold functionalization involves loading scaffolds with angiogenic factors or modifying them to improve porosity and channeling for better perfusion. Cell-based techniques use endothelial cell cocultures or transfection of cells to overexpress angiogenic factors. Bioreactor designs, such as rotating and perfusion bioreactors, enhance nutrient and oxygen transport. MEMS approaches use microfluidic devices to mimic natural vasculature. Modular assembly involves combining endothelialized microtissues to form larger constructs. In vivo systems, like polysurgery techniques and arteriovenous (AV) loops, utilize the body's natural angiogenic potential. The chapter also highlights the importance of quantitative modeling and measurement of oxygen diffusion and consumption within engineered tissues to optimize vascularization strategies. This includes using Fick's law, Michaelis-Menten kinetics, and Navier-Stokes equations to understand oxygen distribution and transport. Overall, the review provides a comprehensive overview of the current state of vascularization techniques in tissue engineering, emphasizing the need for further advancements to achieve clinically relevant vascularized tissues.The chapter discusses the current challenges and strategies in vascularization for tissue engineering. The primary challenge is the limited size of tissue constructs due to nutrient and oxygen diffusion limitations, which restrict the integration of these constructs in vivo. To address this, researchers have explored various approaches, including scaffold functionalization, cell-based techniques, bioreactor designs, microelectromechanical systems (MEMS), modular assembly, and in vivo systems. Each approach aims to improve oxygen and nutrient transport, enhance vascularization, and facilitate integration with host vasculature. Scaffold functionalization involves loading scaffolds with angiogenic factors or modifying them to improve porosity and channeling for better perfusion. Cell-based techniques use endothelial cell cocultures or transfection of cells to overexpress angiogenic factors. Bioreactor designs, such as rotating and perfusion bioreactors, enhance nutrient and oxygen transport. MEMS approaches use microfluidic devices to mimic natural vasculature. Modular assembly involves combining endothelialized microtissues to form larger constructs. In vivo systems, like polysurgery techniques and arteriovenous (AV) loops, utilize the body's natural angiogenic potential. The chapter also highlights the importance of quantitative modeling and measurement of oxygen diffusion and consumption within engineered tissues to optimize vascularization strategies. This includes using Fick's law, Michaelis-Menten kinetics, and Navier-Stokes equations to understand oxygen distribution and transport. Overall, the review provides a comprehensive overview of the current state of vascularization techniques in tissue engineering, emphasizing the need for further advancements to achieve clinically relevant vascularized tissues.