In this communication, we introduced an innovative method to study out-of-equilibrium aqueous solutions using time-resolved low-temperature solid-state NMR. The method relies on the cryofixation of reacting solutions in order to trap and preserve transient reaction intermediates. The aging time is controlled on a tens of milliseconds time scale by a stopped-flow device connected to a freeze-quench accessory, where the cryofixation is ensured by spraying the solutions in cold liquid isopentane at -145°C. Then, the filling of NMR rotors is achieved with specifically designed packing tools ensuring the control of the low temperature during the whole process.