Spheroid microtissues that can mimic native tissue-like structure and function, spheroid production methods that are high-throughput, suitable for efficient production, maintainable over long-term culture, and/or offer repeatable control over size distribution. Spheroids that have blood vessels, including spheroids with functional, blood-perfused vascular networks upon injection in vivo. Dissolvable hydrogel microwell arrays for high throughput parallel formation of spheroids in a single pipetting step and easy retrieval for downstream applications. A method to produce prevascularized microtissues in sufficient numbers to form a macrotissue in vivo for therapeutic purposes. This method is based on sacrificial release of dissolvable microwell templates, a novel and scalable strategy which enables gentle harvesting of microtissues with control over size and composition. The method forms microtissues containing endothelial cells and mesenchymal stem cells, which are co-cultured under dynamic conditions and self-organize into blood-vessel units.
