The chemistry of triazines and tetrazines in 2019 was important in terms of chemistry (synthesis and functionalization) and in terms of applications. s-Triazine is the most studied heterocycle for biological applications and for materials applications, thanks to its C-3 symmetry and its electron-poor character (as organic frameworks and fluorescent materials). Many papers are reported with 1,2,4,5-tetrazines mainly for their use in bioorthogonal chemistry. as-Triazine chemistry deals with a few original syntheses and as usual with inverse electron Diels–Alder reactions. Finally, a few papers on purines, and pteridines are also reported.