Many practical operations, such as environment depollution, blood dialysis or product purification, require matter transfer. With an emphasis on the aforementioned subjects, this book revisits the founding principles of materials transfer on the basis of Fick’s first law, which constitutes the foundation of diffusional phenomena. Additionally, continuity equations translating the macroscopic balances of systems are established. These balances constitute Fick’s second law, which can be applied to quantify the fluxes of matter transferred in each situation, provided physical data is available. To this end, Mass Transfers and Physical Data Estimation pays particular attention to methods of data estimation. Methods presented in this book are applied to several practical cases, such as diffusion in catalytic reactions or the reconstitution of cartilage in human bone joints.