The two different pathways to activate host immature dendritic cells (DCs) into mature antigen-presenting DCs for cancer immunotherapy using mesoporous silica nanoparticles (MSNs) and mesoporous silica microrods (MSRs) are discussed by Jaeyun Kim and co-workers in article number 1803953. MSNs deliver immunomodulators into immature DCs by phagocytosis to active them, while the macroporous scaffold composed of randomly stacked MSRs recruits immature DCs and activates them in artificial microenvironments generated by the scaffold itself.