I don't own these characters.

Summary: Sherlock is stumped by pet names, but as usual he proves that he understands more than people think.

Sherlock was puzzled the first time John called him sweetheart. He knew he wasn't sweet in an emotional sense, and for about a day he worried that John might be contemplating cannibalism. He watched John closely that whole day, determined that the doctor would not find out if his heart was actually sweet in taste.

When John called him honey, he was slightly more open to it. Honey is, after all, a wondrous substance made by very interesting, industrious creatures. Still, it didn't seem quite right.

The one time John called him baby he voiced his objection out loud. He refused to be likened to an infant, no matter who thought it was an apt description.

Finally, he asked John why he couldn't simply call him by his name. He didn't understand why such endearments were necessary, and in some cases he couldn't fathom how they ever became popular.

John told him that pet names were a way to let someone know they were special to you. A name that was only for you to use was, after all, an intimate and familiar thing.

The first time Sherlock called John 'Petri', John shrugged it off, thinking that Sherlock's mind was on something else, like the times Molly told him he called her John.

However, the more times he used it, the more John realized it was deliberate.

One night, when they were sitting in front of the fireplace having some tea, he asked Sherlock why he called him that.

Sherlock paused and looked at him for a moment before telling him that Petri dishes are useful things, good to have around. Sometimes they can be fragile, and sometimes they hold things that don't seem special at first, but when you look closer, those things can be beautiful.

John quietly stood and placed a soft kiss on Sherlock's hair before taking his hand and leading him to the bedroom.

He would tidy up the cooled tea in the morning.