Tissue T1 relaxation is considered to be monoexponential. This is, however, an assumption, since it is seldom measured with sufficiently dense sampling of the relaxation curve. We hypothesized that a spatially-resolved investigation of tissue T1 relaxation curve with ultra-high temporal resolution might reveal previously unidentified characteristics of this fundamental NMR parameter. We imaged 10 healthy volunteers using a Look-Locker sequence with 460 time points 17ms apart on the inversion recovery curve. Denoising using PCA and NNLS decomposition of the recovery curves revealed, among others, a moderately short T1 component (4-500ms) in both WM and GM, tentatively assigned to myelin water.