There are various origin stories for the Fantastic Four, but this is the basic one. The Fantastic Four was a team of scientists and astronauts who were doing an experiment in Space. An accident on return to earth happened. The ship traveled through a Cosmic storm and exposed the team, which were given fantastic super powers and abilities.
In "Ultron-5", Red Ghost with his Super-Apes manages to infiltrates to the home of the Fantastic Four. But arriving he found Black Panther and Hulk, who easily defeat him and his Super-Apes.
In "The Private War of Doctor Doom", The Thing and the Human Torch went to the Avengers Mansion to play cards. Meanwhile, Janet and Tony went to visit Sue and Reed. Doom uses these meetings to attack them simultaneously. Reed did not understand why Doom attack them knowing that they were accompanied by the Avengers. After a fierce battle, Doom decided to release Janet and Sue. It is revealed at the end that the Invisible Woman was replaced by a Skrull.
When the Skrull invasion began, the Invisible Woman (Skrull) sent the Baxter Building to another dimension but the Real Invisible Woman could enter that dimension and return it to its place of origin.
