Colloidal and nanoparticle dispersions can be formulated to exhibit shear thickening, which in extreme form leads to flow jamming at high stresses. This state of the dispersion is characterized by both high elasticity and high energy dissipation, and is a consequence of particle self-organization into “hydroclusters”. These hydroclusters are characterized by flow instability of stress-induced anisotropic particle density fluctuations. Studies of the relationship between the morphology of the hydroclustered state, macroscopic rheology, and particle & solvent properties and interparticle interactions in model and industrial systems elucidate the conditions required to achieve a flow jammed state. Novel applications of shear thickening materials as composite materials for mitigating ballistic, stab, and puncture threats have been demonstrated and are now under commercial development.