Plasma cells are antibody-producing cells and represent the developmental end point of the B-cell lineage. Over the last few years, major progress has been made in understanding the transcriptional regulation of B-cell to plasmacell transition. Two transcription factors, Pax5 and Blimp1, are responsible for the development and maintenance of B-cell and plasma-cell identity, respectively. Both factors regulate mutually exclusive transcriptional programs and are part of a gene-regulatory network that ensures each other's repression. Consequently, it became apparent that pathways must exist that, after B-cell activation, initiate differentiation while at the same time allow clonal expansion, class switch recombination (CSR) and somatic hypermutation. In this issue of the EMBO Journal, Muto et al (2010) report that Bach2 is the transcription factor that regulates the timing of plasma-cell differentiation. Bach2 functions by suppressing Blimp1 expression in activated B cells, thereby opening a time window during which differentiation is delayed and CSR can occur.