Tony rarely thought about the fact that Steve's history meant that there were a lot of things he had no experience with. He'd adapted to the modern world with a speed that made Tony wonder if the super soldier serum had mental effects as well as physical ones.
But every now and then Steve would run into some experience or tech that Tony took for granted. His reactions never failed to make Tony see tired, ordinary things in a new light, but this was the first time that something ordinary made him see Steve in a new light.
Steve's slow, careful first steps into the hot water had made Tony grin in amusement. But as Steve immersed himself his expression transformed into a picture of bliss. He sank down onto one of the submerged benches, leaned back against the rim of the tub, and closed his eyes. His mouth was open a little, his breath deep. The heat of the water brought a flush to his fair skin. After a moment he sighed and sank deeper into the water.
Tony stared, heart pounding, and was very glad Steve's eyes were closed.
Licking his lips unconsciously, Tony reached out to turn on the jets.