Adjuvants are essential for enhancing and directing immunity to vaccine antigens. Most adjuvants in clinical use are particulates, but how they drive innate and adaptive immune responses is unclear. A major recent advance was the demonstration that particulate adjuvants promote activation of the NLRP3 inflammasome. The mechanisms underlying this activation have been partly resolved and the role of NLRP3 in particulate adjuvant-induced adaptive immunity is currently the subject of intense interest.