A quantum spin liquid is a phase of magnetic matter where quantum fluctuations destabilize magnetic order, even at T = 0 K. The rise of exactly solvable models with spin-liquid ground states, coupled with a trove of new materials in which to explore the underlying principles and tune the spin-liquid state, have opened up new horizons in this field. For many spin liquids, their unusual physical properties are determined by a hidden topological order. Unfortunately, the presence of a topological order is not easy to demonstrate experimentally. Building upon our previous advances, we will look for new types of emergent excitations in quantum magnets including the yet-to-be-discovered photons and quantum Dirac monopoles and utilize edges and defects to characterize the underlying quantum spin liquid state, as well as develop new spectroscopies to expose their elusive fractionalized excitations.