Explore non-Hermitian topological corner modes in exciton-polariton lattices under nonresonant pumping in this 40-minute lecture. Discover how signals propagating in the bulk of the system can navigate around defects, a feature not possible in one-dimensional topological lattices or two-dimensional lattices with Hermitian edge states. Examine the system's topological nature in the presence of nonlinear interactions, evidenced by the winding of the complex fluctuation spectrum. Learn about the potential for more accurate measurement of polariton-polariton interaction strength due to the localization of all polariton states, avoiding condensation in states with large overlap with the pump-induced exciton-reservoir.