Dr. Iustinian Bejan is currently CS-II at L3-CERNESIM-ICI receiving the Doctoral degree in 2007 at the University of Wuppertal, Germany acting later as scientific researcher. Dr. Bejan was also the recipient of two prestigious postdoctoral fellowships: IRCSET at University College Cork, Ireland, and MARIE CURIE at the University of Leeds, United Kingdom. The main research area is the study of physico-chemical processes in the atmosphere. The research topics comprise the gas-phase chemical kinetics and atmospheric degradation, and secondary organic aerosol formation from oxidation of VOCs as well as modeling of chemical reactions. The most important contributions consist of the discovery of a new HONO source in the atmosphere, development and validation of new techniques and instruments for measurement of ozone and NOx, detection of nitroaromatics, and measurements of OH and HO₂ radicals on aircraft platforms. A well understanding of the atmosphere is a continuous challenge for Dr. Iustinian Bejan.