The continued success of the jet substructure program at the LHC will require the widespread use of tracking information, to enable increasingly precise measurements of a broad class of observables. Precise theoretical predictions for track-based observables can be obtained using the track-function formalism. I will discuss our recent extension of this formalism to order alpha_s^2, it’s application to energy correlators, the non-linear evolution of track functions and how this acts as "master equation" for (multi-)hadron fragmentation functions.