the hero's bones and the lover's heart-
In the time they've known each other, Booth has learnt things from Bones. Impossible not to, really, the woman exudes knowledge.
The value of empirical evidence is an example—while his side of the job is vital, he's willing to concede now that lab evidence is more than just window-dressing to convince juries of the facts extracted by cops like him. And it's inconceivable to be around Bones for any length of time without learning something about bones. Hell, even Parker's started calling his fingers phalanges. Booth's no squint (will emphatically and vehemently deny this charge to anyone foolish enough to accuse) but bone knowledge seems to drift in by osmosis. Or something.
He doesn't let her realize he knows these things, of course. Doesn't tell her he's aware of what the calcaneus is when she tells him it's the heel bone. Anyway, at crime scenes he's focussed on suspects, victims, circumstances not ugly, mangled, sickening bones. Effectively, he forgets he knows these things, and he and Bones work in their own spheres of expertise.
However, the world viewed through the fuzzy stupor of the recently woken is a very different place. Bones' bones are beautiful. Elegant, symmetrical, perfect, even as she sleeps in his arms and Booth finds he can name all of hers: temporal bone, supraorbital process, parietal bones, frontal bone…
(when we die they can bury us in the same grave and once the flesh decays they won't know whose bones are whose)
(Until another Bones comes along.)
The thought makes him smile as he drifts off again.