Prof. Tuukka Petäjä has over 20 years of research experience related to atmospheric sciences. He leads the experimental aerosol group; educated 27 PhDs to completion and is currently supervising 10 students; He has published over 425 peer reviewed articles (10 in Science, 9 in Nature), total citations 20400, h-factor of 69. He is a highly cited scientist (2014-, Thompson Reuters). He received FAAR Award in excellent aerosol science and Vaisala Award 2013 for his work on combining state-of-the-art science and instrument development; Receiver of Science and Technology in Society Future Leader Award, New York Academy of Sciences, PI of Biogenic Aerosols – Effects on Clouds and Climate (BAECC), multiplatform research campaign to elucidate the role of secondary aerosols to clouds, supported by US Department of Energy. Science director of Pan Eurasian Experiment (PEEX), board member of PACES initiative, academician in International Eurasian Academy of Sciences (IEAS). Managerial expertise: head of technical staff of Kumpula science campus, head of SMEAR infrastructures. He has participated in practical organization of 12 EU projects, Coordinator of iCUPE. Petäjä is a team leader in Finnish Center of Excellence of Academy of Finland on atmospheric sciences responsible for long-term, comprehensive observations in Finland and developing observational capacity in Russia and China. Partner in CAMS_21a, Co-Coordinator of ACTRIS-IMP, which is setting up European-wide harmonized observations on atmospheric trace gases, aerosol particles and clouds (ACTRIS). Head of ACTRIS-Finland, a national contribution to the ACTRIS infrastructure.