Sherlock has like 14 different hair gels and they all have very specific purposes based on the day’s temperature, humidity levels, what sort of plans he has made for the day, etc. Each bottle is labeled and its uses are catalogued in a little notebook he keeps under the sink. The pages are laminated so it doesn’t get all wet and ruined when it’s in the splash-zone (that’s what John calls the rest of the loo when his posh boyfriend is doing his hair). John thinks that this system and all of the time Sherlock has put into organizing it is absolutely adorable. He especially loves the fact that there is one bottle on the shelf labeled only with a heart, which - according to the catalogue - is reserved for “dates with John.” He loves the smell of it. It smells like home.