This Methods Collection focuses on commonly used or newly developed innovative assays to assess and quantitate functional properties of pericytes / mesenchymal stem cells. This issue is open to original and previously published methods to study stem cells or cell-free products. The collection aims to explore interactions between stem cells and endothelial cells in conjunction with inflammation, coagulation, and/or neural innervation to detect and assess levels of microvascular dysfunction. The investigation can be at the tissue, cell, or subcellular levels. Studies utilizing cell lines, mixed cultures, micro-engineered in vitro tissue models, 3D bioprints, and the application of new devices, computer modeling, and simulations are welcome. The readout assays should be practical, quantitative, and reproducible for the potential of future industry adaptations. This special issue is for a call to action on standardizing methodology towards new treatment modalities promoting vascular health and regeneration. It is particularly relevant to the ongoing pandemic for acute and post-infection sequela of COVID-19 and oncologic, ischemic, autoimmune, and metabolic disorders.