Guillermo Villena Tapia joined the IASS in July 2016 as a research associate for the project “Three-Dimensional Observation of Atmospheric Processes in Cities-3DO”. This project is part of the BMBF research programme “Urban Climate Under Change” and focuses on collecting data on air pollution and climate-relevant parameters. Guillermo Villena Tapia obtained his Licentiate Degree in Chemistry at Universidad de Santiago de Chile (USACH), where he studied the chemical composition of hydrometeors (fog, dew, and rain) in highly polluted settings. His Ph.D. was obtained from the Bergische Universität Wuppertal (BUW), working on the development, validation and application of a new long path absorption photometer (LOPAP) for the sensitive detection of NO2. He has successfully collaborated with interdisciplinary research groups in many international projects. During his research work, he became proficient in the use of techniques for the measurement of reactive nitrogen compounds and their application in urban and polar field measurements and laboratory studies. His research interests are environmental analytical chemistry, air quality, atmospheric chemistry, multiphase processes in the atmosphere, and environmental management.