The line of Avengers toys: Endgame revealed a great spoiler: the quantum suits. Iron Man and Captain America appear wearing these clothes, so they would travel in time.
For several months a curious theory has been around for this latest installment of the Avengers, putting an end to Phase Three, in which we talk about possible trips through time. How would they do this? Entering the Quantum Kingdom, a world that was already seen in Ant-Man & The Wasp.
However, in order to enter this universe, the heroes must wear special suits, because not everyone can survive in it. In the case of Ant-Man, Hank Pym and Janet, the three of them shrunk to the size of tiny particles in order to survive.