Anthropogenic emissions of trace gases and aerosols are changing the chemical composition of the atmosphere, which in turn gives rise to major environmental challenges. Air pollution from trace gases and aerosols has severe health impacts on people living in urban areas. Infrared radiative forcing due to the emission of trace greenhouse gases, including CO2 and methane, results in global warming, global sea level rise, droughts, etc.. And trace emissions of species responsible for the destruction of stratospheric ozone risks exposure to harmful UV radiation. Measuring these species and their impacts presents a scientific challenge as well, because some of the emitted trace gases and aerosols are short-lived and have therefore a local or regional impact, while other species are long-lived and have a global impact. To address these challenges, the Tropospheric Monitoring Instrument (TROPOMI) on board the European Sentinel 5 Precursor satellite, launched in October 2017, is capable of monitoring atmospheric composition both at high spatial resolution as well as globally, and to monitor changes over different timescales. This colloquium will describe the measurement principles of TROPOMI, and how its wide spectral range, global coverage, and fine resolution provide great opportunities for scientific data exploitation and near-real time applications.