I will discuss universal structure associated with information spreading in chaotic systems. The aim of the talk will be to explain how this structure emerges (after coarse-graining) in "realistic" translationally invariant systems, as opposed to analytically tractable model systems. Model systems built from random unitaries allow analytical calculations via an explicit average over random unitaries; this approach is evidently not available for Hamiltonians without randomness. We explain why the same key universal structures, involving pairing of spacetime trajectories, appear nevertheless, and give a formalism for calculations in generic Floquet chains. Work with Tianci Zhou (https://journals.aps.org/prx/abstract/10.1103/PhysRevX.10.031066)