Time-lapse to assess NRTS. Paired-cell assays were performed on R1-derived EBs 7 d after differentiation using the CldU/IdU double-labeling method. Cells were plated at clonal density, and the second division was followed by time-lapse microscopy. Cells were immediately fixed and immunostained for CldU and IdU. Differential interference contrast (DIC) images and DAPI nuclear counterstaining are shown. (a and b) Representative photographs of symmetric (a) and asymmetric (b) daughter cells are displayed, and CldU fluorescence intensity (normalized to IdU intensity) distribution among daughter cells is shown. (c) Photographs of the first time-lapse image acquired for Videos 6 and 9 unambiguously showed that a single cell was plated. Time-lapse videos corresponding to each set of photographs presented in a and b are specified in the right column.