Inhibiting transcriptional elongation is a recurrent mechanism to keep cells in an undifferentiated, pluripotent state in metazoans. It remains, however, unclear whether lifting the barrier to transcriptional elongation acts as the switch to initiate differentiation in those organisms. Recent results suggest that such a mechanism for turning on differentiation does exist in plants. We argue that targeting the elongation phase of transcription may be a solution adopted widely in evolution to allow for the global transcriptional changes needed in cellular differentiation.