The planetary boundary layer is the lowest part of the Earth's atmosphere, extending from the surface up to a height of a few hundred to a few thousand meters. It is characterized by turbulent mixing of air and is strongly influenced by surface processes such as heating and cooling, friction, and topography. Research in the planetary boundary layer focuses on understanding and predicting its dynamics, structure, and interactions with the surface. This includes studying how different factors such as temperature, humidity, wind, and pollutants are transported within the boundary layer, as well as how they impact weather, climate, air quality, and other environmental processes. Researchers use a combination of observational data, numerical models, and theoretical analysis to investigate the complexities of the planetary boundary layer and improve our ability to forecast and manage atmospheric processes. Overall, this research area plays a crucial role in improving our understanding of the Earth's atmosphere and its interactions with the surface environment.