Dendritic cells (DC) are a class of bone-marrow-derived cells that serve as an interface between innate sensing of pathogens and activation of adaptive immunity. Three major DC subsets—plasmacytoid DC (pDC), myeloid/conventional DC1 (cDC1), and myeloid/conventional DC2 (cDC2)—are distinguished by their unique transcriptional profiles and functions. pDC are specialized in producing type I interferons, while cDC1 and cDC2 are involved in antigen presentation and immune activation. DC development is regulated by a complex network of transcription factors, including IRF8, IRF4, and BATF3. DC haematopoiesis is conserved across mammals and distinct from monocyte development. Recent advances in transcriptomics and flow cytometry have enabled the identification of new DC subsets and markers, enhancing our understanding of DC function in vivo. The classification of DC subsets is based on lineage, with cDC1 and cDC2 being distinct from monocyte-derived DC (mo-DC). The development of DC is influenced by various transcription factors and signaling pathways, including those involving IRF4, KLF4, and NOTCH2. DC subsets play critical roles in immune responses, including the recognition of pathogens, antigen presentation, and the regulation of immune cell activation. The functions of DC subsets vary, with pDC being specialized in interferon production, while cDC1 and cDC2 are involved in cross-presentation and T cell activation. Langerhans cells, a subset of DC, are found in the epidermis and other epithelial tissues and play a role in immune surveillance. Monocyte-derived DC (mo-DC) are involved in inflammatory responses and can be found in various inflammatory conditions. The study of DC subsets has important implications for understanding immune function and developing new therapeutic strategies.Dendritic cells (DC) are a class of bone-marrow-derived cells that serve as an interface between innate sensing of pathogens and activation of adaptive immunity. Three major DC subsets—plasmacytoid DC (pDC), myeloid/conventional DC1 (cDC1), and myeloid/conventional DC2 (cDC2)—are distinguished by their unique transcriptional profiles and functions. pDC are specialized in producing type I interferons, while cDC1 and cDC2 are involved in antigen presentation and immune activation. DC development is regulated by a complex network of transcription factors, including IRF8, IRF4, and BATF3. DC haematopoiesis is conserved across mammals and distinct from monocyte development. Recent advances in transcriptomics and flow cytometry have enabled the identification of new DC subsets and markers, enhancing our understanding of DC function in vivo. The classification of DC subsets is based on lineage, with cDC1 and cDC2 being distinct from monocyte-derived DC (mo-DC). The development of DC is influenced by various transcription factors and signaling pathways, including those involving IRF4, KLF4, and NOTCH2. DC subsets play critical roles in immune responses, including the recognition of pathogens, antigen presentation, and the regulation of immune cell activation. The functions of DC subsets vary, with pDC being specialized in interferon production, while cDC1 and cDC2 are involved in cross-presentation and T cell activation. Langerhans cells, a subset of DC, are found in the epidermis and other epithelial tissues and play a role in immune surveillance. Monocyte-derived DC (mo-DC) are involved in inflammatory responses and can be found in various inflammatory conditions. The study of DC subsets has important implications for understanding immune function and developing new therapeutic strategies.