We discuss the role of atmospheric aerosols and their interactions with clouds. Aerosols play an important role in the global radiative budget of the atmosphere: they can directly interact with solar and terrestrial radiation, and modify microphysical and radiative properties of clouds. Quantifying the aerosol impact on clouds is of fundamental importance since clouds cover about 60% of the Earth's surface and are an important regulator of the global radiative budget. However, the uncertainties of aerosol-cloud interactions are still very large. The fundamental tools used to enhance our understanding of climate system are numerical models that simulate the entire atmosphere (global models). Such models are continuously developed in order to improve the representation of the Earth System and they allow for the estimation of the anthropogenic influence on climate. In this context, we pay particular attention to the parametrization of ice clouds in the EMAC model. In the final part of the talk we review some relevant information regarding the application for a PhD position. How to search for a PhD position? When? What are the qualifications required to the applicants? Which documents have to be submitted?