Literature
When it happens...
When they do get together, it starts slowly. Neither John nor Sherlock would like to admit it, but they are both nervous and scared. But also excited, and giddy even, though neither will ever admit it.
It starts with very small things, John will cook for them without being asked every now and then, or occasionally Sherlock will play John's favorite tunes on the violin. John doesn't complain about the various body parts in the fridge so much anymore, and Sherlock stops implying that John has a low intellect, which isn't even true.
When it starts to get physical, Sherlock quietly admits he's never been with someone that way before. It's new