He'd been through it once before and the sound he'd made that time still echoed in his dreams. But of course a refresher was welcome compared to the alternative, being trapped in his smaller body forever. It hurt too much to completely comprehend what was happening, but once it was done it didn't linger and Steve breathed deep right into the bottom of his lungs.
It felt incredible and Steve wouldn't take breathing for granted ever again. Tony looked a little like he might go into shock and Steve ran his hand up and down his own arm just to check, to be sure.
Steve glanced down, glad that the seams had held and he hadn't embarrassed himself out in a public place. "Huh, fancy that," he said as he looked back up at him. Steve moved forward on his knees until he was in front of Tony and pulled him up off his ass and into his arms, his face pressed against his neck.