He knows your favorite color and your eye color. He knows how you wear black all the time.
More importantly, though, he knows how you like dumb jokes and puns and puns about science. He knows how you love theatre and singing and randomly bursting out into song. He knows how you hate Christmas music with rapping in it.
He knows your problem with sudden change without warning. He knows about your OCD. He knows how you hate bad grammar. He knows how it irritates you when he uses double negatives on purpose to make you mad.
He knows your love for books. He knows your insecurities and what gives you anxiety.
Most importantly, from your little habits like closing drawers behind people to the way you can make a reference out of anything, he knows he loves every bit of you.