Plasmacytoid dendritic cell precursors (pDC/IPC) are the major producers of type I interferon and have the unique ability to link innate and adaptive immunity. After producing large amounts of type I IFN in response to microbial stimulation, they can differentiate into DC capable of stimulating naive T cells and modulate the adaptive immune response. In this review, we focus on the transition between these two highly specialized cell types, which is accompanied by major morphological, structural and functional changes, many of which remain to be fully characterized. We propose that the plasmacytoid and dendritic morphologies correspond to distinct differentiation states and effector functions.