FACS-sorted EB cells were washed in cold PBS, counted and aliquoted (50,000 live cells). For the Tn5 transposition reaction, the Omni-ATAC protocol was used with some modifications. Briefly, cells were lysed and then resuspended in transposition reaction buffer (50% TD Tagment DNA buffer and 5% TDE1 Tagment DNA enzyme in PBS) for 30 minutes. ATAC-sequencing libraries were generated using the Nextera Index kit (Illumina) and sequenced (75 base pairs, paired end)