This project aims to understand Lagrangian transport and mixing of substrates in reactors to prevent zones of poor mixing and to tailor the mixing process. 3D Lagrangian particle tracking measurements and decolorization experiments are conducted resulting in highly resolved Lagrangian data and mixing time distributions for different classical reactor types. Novel computational Lagrangian methods allow us to extract transient transport patterns, i.e. moving volumes with certain mixing abilities from these data sets. Finally, measurements and analysis are extended to structured reactors and to the context of trajectories of Lagrangian sensors that do not exactly follow the flow.