Paolo Pesaresi has 20-year experience in plant molecular biology, molecular genetics, biochemistry and plant physiology. During this period, he has significantly contributed to the elucidation of the molecular mechanisms responsible of the short-term regulation of photosynthesis. The discovery of the STN7 and STN8 kinases (Nature, 2005, 437: 1179-1182; Plant Cell, 2009, 21: 2402-2423) and the identification of the TAP38 phosphatase (Plos Biology, 2010, 8: e1000288) has clarified the molecular mechanisms that underpin the “State Transition” mechanism and the turnover of the Reaction Center of photosystem II, under fluctuating light conditions. Furthermore, the characterization of the PGRL1a and PGRL1b thylakoid protein subunits has revealed the existence of the long-sought thylakoid protein complex, responsible of cyclic electron transport around photosystem I (PSI) (Cell, 2008, 132: 273-285; Molecular Cell, 2013, 49: 511-523). More recently, he has dedicated his efforts to the elucidation of the molecular mechanisms responsible of the chloroplast-to-nucleus communication, i.e. retrograde signaling pathway, necessary to coordinate plastid- and nuclear-gene expression in response to environmental changes and physiological-developmental needs. He was the first to reveal the existence of synergistic effects between chloroplasts and mitochondria, altered in organelle protein synthesis, with respect to changes of nuclear gene expression (Plant Cell, 2006, 18: 970-991), and subsequently he and his group has contributed to reveal the involvement of GUN1 protein in the maintenance of chloroplast protein homeostasis (Plant Physiology, 2016, 170: 1817-1830; Front. Plant Sci., 2016, 7: 1427; Plant Physiology, 2018, 176: 634-648). The research group is also involved in transferring basic knowledge obtained from studies in Arabidopsis thaliana to crops such as rice, as shown by the characterization of the OsPSTOL1 protein (Nature, 2012, 488: 535-539), barley (see the BarPLUS project, http://faccesurplus.org/research-projects-1st-call/barplus/) and grapevine (see the GrAptaResistance project, http://sites.unimi.it/graptaresistance/).