Different differentiation tendencies between cells located at the periphery and center (spatial heterogeneity) of the PSC colony indicated by the image streams. The 0–72 h bright-field images were enhanced and shown in inverted color for a clearer colony edge. After CHIR treatment, PSC colonies start to contrast at 0 h; starting from ~24–48 h, cells located at the periphery of the colony migrate into the cell-free region (circled in time-lapse images of the first row as an example) until the whole well was filled at ~72 h. This group of migrating cells is likely to successfully differentiate, while the cells located at the center of a large colony tend to fail. Scale bar, 1 mm.
