This paper is written by experts in the field and addresses new tropospheric chemical mechanism developments. It shows how new analytical methods, instrumentation and cheminformatics methods have led to the identification of key processes and knowledge gaps in our understanding of chemical mechanisms, both in the gas phase and condensed phases. The opinion paper presents a perspective on these developments in the present and future, and outlines new directions. This opinion will be a very valuable contribution for the community and I am convinced it will be frequently read and cited.