The Muon Ionization Cooling Experiment (MICE) has measured the change in emittance due to ionization energy loss. Large aperture solenoid magnets were used to focus muons through Lithium-hydride, liquid hydrogen and empty absorbers. Diagnostic devices were placed upstream and downstream of the absorber, enabling the phase-space coordinates of individual muons to be reconstructed. By observing the properties of ensembles of muons, the evolution of the beam emittance was studied. The phase-space was analysed using single particle amplitude distributions and shows a clear increase in the core density of the beam, a direct effect of ionization cooling.