It is well-known that isocyanates and water yield polyureas; however, that reaction is not generally associated with the synthesis of the latter, being used instead for environmental curing of films baring free NCO groups or for foaming polyurethanes. Here we report that careful control of the relative isocyanate/water/catalyst (Et3N) ratio in acetone, acetonitrile, or DMSO prevents precipitation, yielding instead polyurea (PUA) gels convertible to highly porous (up to 98.6% v/v) aerogels over a very wide density range (0.016−0.55 g cm−3). The method has been implemented successfully with several aliphatic and aromatic di and triisocyanates. PUA aerogels have been studied at the molecular level (13C NMR, IR, XRD), the elementary nanoparticle level (SANS/USANS), and the microscopic level (SEM). Their porous structure has been probed with N2-sorption porosimetry. Despite that the nanomorphology varies with density from fibrous at the low density end to particulate at the high density end, all samples consis...