Quantum magnets are a natural source of new quantum states of matter encompassing different types of spin liquids, crystals of topological solitons and magnetically ordered states with non-classical spin dynamics. Remarkably, this complexity emerges from competing interactions between spin degrees of freedom, that are the basic building blocks of quantum magnets. Neutron scattering probes are key for detecting and characterizing these novel states of matter because they excite magnetic modes with arbitrary wave length ranging from one to hundreds of lattice spaces.