NMR relaxometry data analysis is presented in the context of a study of a few complex molecular systems like those presenting nematic and smectic liquid crystal phases, confined liquid crystals, and magnetic ionic liquids. The examples include different molecular structures, local molecular organization levels, phase structures, and spin interactions. The multidimensional character of the model fitting procedures required to make possible to obtain a detailed insight of the molecular dynamics in those
systems is described in relation to the use of an open access web fitting platform.