"The formation of aerosol nanoparticles by vapour nucleation and condensational growth is currently considered the dominant source of cloud condensation nuclei on global scale, hence impacting radiative properties of the atmosphere and precipitation patterns of clouds. Despite considerable experimental and theoretical efforts, the mechanisms of the gas-to-particle conversion are still poorly understood, and so are the parameterizations of this process in climate models. Improving the situation critically depends on the continuous development of experimental techniques. For the quantitative characterization of nanoparticle dynamics especially time resolution deserves more attention. I am thus proposing to design instruments that will improve time resolution by up to five orders of magnitude. Specifically, I am planning the design of a fast-scanning electrical mobility based nanoparticle spectrometer delivering size distributions from 1 nm upwards at 1 Hz, for number concentrations as low as 100 cm-3. Secondly, in a new approach to the study of secondary organic aerosol formation I am planning to apply small angle x-ray scattering providing direct information on particle size and number at sub-millisecond time-resolution. Thirdly, the study of fundamental growth kinetics by Mie scattering at short wavelengths will constitute an important part of my research. And finally, an application oriented research task will deal with the design and construction of a nucleation based trace-gas removal system capable of generating liquid water from plain ambient air.The research on phase transition processes constitutes a vital link between molecular scale interactions and macroscopically relevant outcome. The current proposal aims at identifying and quantifying nanoparticle formation mechanisms by new experimental approaches. Thereby it will be possible to reliably predict and utilize macroscopic effects caused by aerosol mechanisms on the nano-scale."