Of the established Ca2+ mobilizing messengers, NAADP is arguably the most tantalizing (1). It is the most potent, often working at low nanomolar concentrations. Unlike other Ca2+ mobilizing messengers, such as inositol trisphosphate (IP3) and cyclic ADP-ribose, which release Ca2+ from the endoplasmic reticulum, NAADP mobilizes calcium from acidic stores, including lysosomes, representing a new function for this organelle. Recent work has implicated a new class of ion channel, the two pore channels (TPCs), as key components for NAADP-evoked Ca2+ release (2). These channels are endolysosomal in localization where they play a role in local Ca2+ release. Three distinct aspects of the NAADP-mediated Ca2+ signalling pathway have been identified. The first is to regulate local Ca2+ release that may play a role in endolysosomal functions, including fusion and trafficking. The second is to trigger global Ca2+ release by recruiting Ca2+-induced Ca2+ release (CICR) channels at lysosomal-endoplasmic reticulum interfaces. The third is to regulate plasma membrane excitability by the targeting of Ca2+ release from sub-plasma membrane stores to activate plasma membrane calcium-activated channels. In this talk, I will discuss the emerging role of endolysosomal-based NAADP-mediated Ca2+ release as a widespread trigger for intracellular calcium signalling in health and disease, and how studies of TPCs have enhanced our understanding of this process.