This chapter provides an overview of studies wherein chemical reactions were used to transform molecules with nuclear spin singlet state overpopulation. In cases of sufficiently high molecular symmetry, these states are not directly detectable. Symmetry-switching chemical reactions have been developed and implemented and were used in order to transform molecules such that the undetectable states become detectable. With this approach, the properties of the originally invisible states could be measured. Particular focus of some recent work has been on the study of potentially long-lived states and the factors that limit their lifetimes. Suitable symmetrisation/desymmetrisation schemes could also enable applications where a readout reaction is used as part of a triggered detection scheme for otherwise invisible (and potentially long-lived) states.