T‐cell development primarily occurs in the thymus and involves in the interactions of many important transcription factors. Until recently, no single transcription factor has been identified to be essential for T‐cell lineage commitment or maintenance of T‐cell identity. Recent studies have now identified the zinc finger transcription factor Bcl11b to be essential for T‐cell development and for maintenance of T‐cell identity. Remarkably, T cells acquire NK cell properties upon Bcl11b deletion. These reprogrammed cells have unique properties in proliferation, cytokine dependency and killing target cells, and may therefore provide a new cell source for some cell‐based therapies.