The name of the story was borrowed from the scientist Paul Zak; you'll be able to guess why once you've read it.
It's basically a shameless excuse to write fluff.

Dean had long since accepted that he probably wouldn't ever completely understand Cas, and that was alright, really. He didn't need to, they got along anyway most of the time, even if he needed to give an occasional nudge in the right direction when it came to matters concerning human interaction. Or, well, angel-human interaction, as it was.

Like, for example, right now.

"Um," he said, eloquently. "Are you, uh, okay?"

Cas had popped into the room, glanced around, nodded contently when he had seen Dean was alone, and proceeded to step up to the hunter to wrap his arms around him.

And he hadn't let go since.

"I'm fine, Dean," he said sombrely, his voice slightly muffled from where he was resting his head on Dean's shoulder.

The hunter nodded, still slightly tense. "Alright. That's good, then. Do you think you could... let go now?"

"No."

Dean blinked at the simple, matter-of-fact reply and sighed, his shoulders relaxing a bit in the process despite himself. "And... why not?"

"I am not done yet," Cas answered in his usual, matter-of-fact tone.

Well. That explained exactly nothing.

The hunter brought up his hands uncertainly and placed them on Castiel's lower back, patting lightly. The angel was very... warm. And he smelled good, though Dean couldn't really pinpoint what the scent was. It was strangely calming, in a way.

"Ah," he made, as if he understood, which he didn't.

Well, they were alone, where was the harm?

He wrapped his arms around Cas properly and rested his temple on the angel's tousled hair, closing his eyes. It was for Cas, after all, he told himself. Maybe it was an appropriate thank-you for everything he had done for them. God knew (hopefully) he deserved it.

Plus, he had to admit that it was actually quite relaxing. Weird, sure, but not necessarily in a bad way. Maybe, after everything that had happened, Cas just needed this. Hugging him wasn't exactly a hardship either, he had the perfect size and seemed relaxed, trusting, like he felt safe.

The feeling was wonderful.

It was strangely disappointing to have Castiel step away suddenly and Dean dropped his arms to his sides, then buried his hands in his pockets. Cas was staring at him with his head tilted to the side in the oh-so-familiar quizzical little gesture, and he seemed content with what he saw. Dean swore he spotted a little smile on his face.

"So," he asked, eyebrows raised and mirroring the smile without really noticing, "what was that about?"

"I was told that a hug only reaches its full capacity of comfort," the angel informed Dean gravely, "when it is held for about twenty seconds." The hunter blinked. "Do you feel comforted, Dean?"

Oh. This hadn't been about Cas, it had been about him all along. Dean felt just a tiny bit slow right now.

"I, uh..." The hunter cleared his throat and shrugged while he pushed down his first automatic response, which consisted of protesting against any sort of touch between two guys that lasted this long. What was done was done, after all. And now that he thought about it... "Yeah, actually," he admitted. It wasn't like Cas was gonna tell on him or anything. "It's, uh... it was great. Thanks, I guess."

Castiel nodded sagely. "You're welcome," he answered. After a second of contemplative silence – he seemed almost nervous – he added: "We could do it again, if you'd like. Later."

Dean swallowed the protest that was on the tip of his tongue and pursed his lips, clearing his throat again. He thought about a gentle way to tell Cas that it really wasn't something two men usually did just like that, even though Cas was technically not male and it wasn't like there was much that was usual about the angel anyway, and...

Aw, what the hell.

"Sure," he replied. "I'd like that."

I'm considering doing a Sabriel version of this... would anyone be interested?