The James Webb Space Telescope has shown us that we cannot consider exoplanet atmospheres as globally uniform objects in chemical equilibrium. On the contrary: day and night sides can have a completely different composition and disequilibrium effects such as mixing and photochemistry will affect chemical abundances, and hence, our understanding of how these planets were formed.

In this talk, I will present new chemical models that incorporate disequilibrium chemistry and three-dimensionality in hot Jupiter atmospheres. I will show that photochemistry can have a global impact and may explain some enigmatic observations on ultra-hot planets. Finally, I will discuss the important effect that photodissociation and ionization have on the atmospheric structure of exoplanets.