Abstract: This presentation shows the results of recent work developed to identify precursors and mechanisms of Biogenic Secondary Organic Aerosols (BSOA) formation in atmospheric-relevant conditions, combining chamber experiments and atmospheric observations within the scope of three distinct sites, namely at the University of Sao Paulo campus, Rambouillet forest near Paris and in Central Amazon. Through the usage of a deployable Proton-Transfer-Reaction Mass Spectrometer (PTR-MS) coupled with an aerosol inlet, molecular distribution of gas and particle compounds can be estimated, as well as compared with current models, such as Two dimensional Volatility Basis Set (2D-VBS). Furthermore, distinct signature spectra have been identified on the most abundant biogenic aerosol precursors, namely Isoprene (through IEPOX and non-IEPOX), Monoterpenes (MT) and Sesquiterpenes (SQT). Application of those identified spectra on the ambient database has allowed the quantification and time variability of each of those sources, yielding for example IEPOX-SOA to be the dominant type in Central Amazon, followed by MT (35%), SQT (13%), and finally Isoprene NON-IEPOX (9%). Further studies include increasing the database of BSOA precursors/pathways as well as anthropogenic species. Quantifying the sources and formation processes of secondary species in the atmosphere is key towards improving climate and air quality models.