(A) Schematic representation of workflow for isolating and imaging organoids in device. (B) Schematic side- and end-view of microvessel device during fabrication and culture. Tumor organoids embedded in collagen I are seeded around a metal rod. After gellation, the rod is removed, the channel is perfused with fibronectin-containing media, and endothelial cells are seeded. Flow is kept at 1 mL/hour, with shear stress of 4 dynes/cm2. (C) Schematic of imaging of the mid-plane of the vessel. (D) Confocal images from a 3D reconstruction of an engineered vessel stained with β-catenin (green) and DAPI. (E) Image of tumor organoids (red) embedded in collagen-I, surrounding a vessel (green). (F) Inset showing a 3D confocal reconstruction of tumor organoids near a vessel. Arrow = direction of flow. Scale bars: 50 μm (D) and 150 μm (E)