CLOUD-DOC is to establish a network of early stage researchers (ESRs, all PhD students) at 12 institutions across Europe (10 EU-funded). The role of aerosol nucleation for atmospheric aerosol, clouds and climate is investigated. The focus of investigations will be to study under well-controlled laboratory conditions the oxidation chemistry, aerosol nucleation and growth processes that are responsible for aerosol particle formation in cold regions of the atmosphere: a) Arctic environments, b) the upper troposphere above the Asian monsoon region, c) the upper troposphere above tropical rain forests, and d) the Southern Ocean. The major research activity of the network will be two sets of joint experiments carried out at the CLOUD aerosol chamber at CERN to which all ESRs contribute. At the CLOUD chamber nucleation experiments are performed at an unprecedented level of precision and completeness using highly innovative instrumentation. A well-structured research and training plan is set up for every ESR as well as a comprehensive, quality-controlled supervision. A high-quality PhD training is arranged. The ESRs are brought together for network training events such as summer schools and workshops for integral data analysis. Courses by world-leading experts are taught spanning from general atmospheric aerosol chemistry and physics to specialized sessions including the role of aerosol for clouds, climate and also health. The summer schools and workshops are specifically tailored to the needs of the trainees. Transferable skills training includes courses on scientific writing, presentation skills, interaction with media, entrepreneurship, IPR, management, gender dimension and diversity in science, and good scientific conduct. The partners from the private sector (1 beneficiary, 4 partners) are closely integrated in the action.