Conventional dendritic cells (cDCs) are sentinels of the mammalian immune system that sense a wide range of danger and homeostatic signals to induce appropriately targeted T cell immune responses. Traditionally classified into two main subsets, cDC1 and cDC2, recent research shows that cDC2s exhibit significant heterogeneity and can be further subdivided. Studies in mice and humans show that, beyond their ontogeny, cDC2s acquire dynamic and tissue-specific characteristics that are influenced by local environmental signals, which impact on their functions during homeostasis, inflammation, and infection. The novel concept is proposed that tissue-derived signals and tissue plasticity can override preestablished developmental programming, thereby redefining developmental trajectories and cDC2 functionality. Ultimately, understanding cDC2 heterogeneity and plasticity has important implications for modulating T cell immunity in health and disease.