(a) Comparison of A/B compartmentalization in B cells (representative experiment shown) and replication timing in a B cell line (CH12 Repli-chip data obtained from the ENCODE consortium) for chromosome 2. Note the extremely high correlation between positive PC1 values (i.e. A compartment domains) and positive replication timing signal (i.e. early replication timing domains). (b) Residence time of switching 100kb genomic bins in either the A or B compartment (as measured in timepoints during reprogramming). See Methods for a detailed description of the analysis procedure employed.