(a) Developing renal organoids are placed on an engineered extracellular matrix (ECM), housed within a perfusable millifluidic chip, and subjected to controlled fluidic shear stress (FSS), note organoids not drawn to scale. (b) Enhanced peripheral vascular network formation in adherent compared to non-adherent underlying ECMs, scale bars = 100 μm. (c-e) Immunostaining of whole mount organoids and (f-g) representative phase contrast images of entire organoids cultured under high FSS (days 12–21), scale bars = 50 μm and 300 μm, respectively, where perfusion direction is left to right. (i-l) Confocal 3D renderings for vascular markers in whole-mount organoids cultured under static U-well, static on engineered ECM, low FSS, and high FSS, scale bars = 100 μm. (m) Angiotool output, which quantifies the abundance and character of vasculature, reported as a fold change relative to the U-well condition. For (m), biological replicates of 8, 11, 6, and 10 were used per condition (U well, Static, Low Flow, and High Flow, respectively) in experiments using both iPSC- and hESC-derived organoids where the entire organoid represents one replicate (one dot) and mean +/− std is plotted. (n) qPCR depicting increased PECAM1 expression under high FSS. The graph is plotted with mean +/− std. Dots on the bar chart represent three technical replicates on RNA pooled from 6 organoids (biological replicates) per condition. DAPI: 4’,6-diamidino-2-phenylindole, PECAM1: CD31, MCAM: CD146, KDR: FLK1, PODXL: podocalyxin, CDH1: E-cadherin, CHIR: CHIR99021, FGF9: fibroblast growth factor 9, FBS: fetal bovine serum. Statistical analysis for (m) and (n) is performed using GraphPad Prism 7 and statistical significance is determined at a value of p < 0.05 as determined by a 1way and 2way ANOVA, respectively, using Tukey’s multiple comparisons test. Different significance levels (p values) are indicated with asterisks as such: *p<0.05, **p<0.01, ***p<0.001.