Microcavity polaritons have demonstrated their unique propensity to host macroscopic quantum phenomena. While they appear to be highly promising for applications in a classical realm, they are still far from competing even with decade old electronics. Another playground where polaritons could emerge as strong contenders is the microscopic quantum regime with single-particle effects and nonlinearities at the one-polariton level. Several theoretical proposals exist to explore polariton blockade mechanisms, realize sophisticated quantum phase transitions, implement quantum simulations and/or quantum information processing, thereby opening a new page of the polariton physics when such ideas will be implemented in the laboratory.