So just how did Scott Lang escape the Quantum Realm, when Janet Van Dyne could not? So far, there are two possible clues. The first is that, when Scott entered the Quantum Realm in the post-credits scene, Janet gave him an important piece of advice; "Don't get sucked into a time vortex," she told him. "We won't be able to save you." In science fiction, a "time vortex" is usually an elaboration of Einstein's theories, and is often used to travel through time and space. A scientist like Janet would know better than to jump into a time vortex in order to escape the Quantum Realm; she'd be well aware that she could wind up anywhere, or any-when, potentially on any plane of existence. But Scott Lang isn't quite so smart, he's a lot clumsier, and he's willing to take crazy chances. He could conceivably either stumble into a time vortex, or actually choose to dive into one. It's worth remembering that Scott is wearing the Ant-Man suit, which means that if he winds up in the wrong place in time or space, he could simply shut down the regulators and shrink back down until he enters the Quantum Realm to try again with another time vortex.
There's a second important clue, though; in the Avengers: Endgame trailer, he drives up to the Avengers compound in a very distinctive van. It's Hank Pym's, and it contains a portable Quantum Tunnel. Now, it's true that the post-credits scene of Ant-Man & the Wasp strongly implied that the Quantum Tunnel could only be operated from the outside, but it's not difficult to imagine the possibility that Pym had built a failsafe of some kind, in case something went catastrophically wrong. So it's quite possible that van could still be Ant-Man's way out of the Quantum Realm.
At this stage, there's little concrete evidence to support either possibility. At the same time, though, the former is the most interesting in that there's an abundance of evidence supporting the notion that Avengers: Endgame involves time travel.
⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀ ⠀⠀⠀⠀ ⠀⠀⠀⠀ ⠀⠀⠀⠀ ⠀⠀⠀⠀ ⠀⠀⠀⠀ ⠀. . . 𝐓𝐡𝐞 𝐂𝐡𝐢𝐥𝐝𝐡𝐨𝐨𝐝 𝐨𝐟 . . . ⠀⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀ ⠀ ⠀⠀ ˋ 𝐄 𝐃 𝐃 𝐈 𝐄 𝐁 𝐑 𝐎 𝐂 𝐊 ˈ ‧ ༚ ⠀⠀⠀ ⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀ ⠀⠀Eddie Brock was something while growing up. He was a child who needed guidance, who needed friendship, who needed love. Right after coming out of the womb, his mother died on the spot in the delivery room due to complications. The second her heart monitor dropped, Carl Brock showed nothing but resentment toward his newborn son, for killing the woman he loved. This was only the beginning. Through out his youth, Eddie’s older sister Mary felt nothing but hate for him, blaming him for killing their- no...her mother. Eddie would try making friends with kids in the neighborhood, but they treated him like an outsider, pushing him around or beating him up, when all he intended to do was introduce himself. All Carl did was throw money at him to get him everything he ever wanted. Everything but the love and attention a child needed. As Eddie would grow older, Mary began to finally adjust to her baby brother, giving him the long waited love Eddie missed. All Eddie ever wanted was his father’s approval, doing everything he could for that approval, such as doing excellent in school and playing sports. Nothing could change Carl’s views on his own son, so Eddie figured he stop trying, which only left him heartbroken. It was then finally Eddie made a friend, his very first to be exact. In elementary school, Eddie would soon meet Peter Benjamin Parker, quite an interesting fellow, a smart one too, but he and Eddie just clicked, remaining as best friends ever since. Soon before hitting High School, young Eddie has had various moments through out the Marvel Cinematic Universe, meeting people, some even powerful than others, but let’s dive in to what exactly Eddie has been through. ⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀⠀⠀⠀⠀⠀ ⠀⠀⠀⠀ ⠀⠀⠀⠀ ⠀⠀⠀⠀ ⠀⠀⠀⠀ ⠀[...𝐂𝐎𝐍𝐓𝐈𝐍𝐔𝐄𝐃 𝐈𝐍 𝐂𝐎𝐌𝐌𝐄𝐍𝐓𝐒...]