Mesoscale convective systems (MCSs) account for over 50% of annual precipitation in large areas of the tropical oceans and in many land regions such as the Sahel, South America, and the central U.S. With intense convection and large stratiform areas, MCSs produce strong and top-heavy latent heating that plays major roles in global and regional circulation. Tracking of MCSs in observational datasets at high temporal (hourly) and spatial (4-10 km) resolution has resulted in regional and near-global MCS tracking datasets that enable advances in MCS research in many directions. Besides revealing the observational characteristics of MCSs such as their intensity, frequency, convective and stratiform areas, lifetime, propagation, and diurnal and seasonal variability, MCS tracking data can be combined with other datasets to facilitate research on the environments that support MCS initiation, land-atmosphere interactions associated with MCSs, interactions between MCSs and the Madden-Julian Oscillation (MJO), the roles of MCSs in flooding, and other topics. Furthermore, applying MCS tracking to model simulations has motivated the development and use of more process-oriented metrics and diagnostics to understand model biases in simulating MCSs. In this presentation, I will highlight a few examples of research facilitated by MCS tracking and insights gained on the many facets of MCSs and their roles in the hydrological cycle and regional and global climate.