The video garnered more than 15 million hits in a couple of days, so chances are you might've seen it already. But even if you haven't, it's more than likely you can imagine pretty clearly what Mia's doing, and what Mia sounds like. If you watch the corner of the internet known as "Make-up YouTube", you already know. Trust me.

Because here's the thing: Mia is speaking in the very specific and codified language of YouTube beauty tutorials.

It's all there. The sibilance of her speech (she smacks her lips together in the way only 4-year-olds and YouTubers do); the "gameshow assistant" presentation pose; the way she touches her hair and splays her fingers before steepling her hands. At four years old, Mia has understood and internalised a complex series of rules of what it means to be creating a YouTube video for public consumption. She is the star of this video, in the same way the biggest, highest-earning vloggers are the stars of the hundreds and thousands of videos hosted on the platform.

Mia is not just acting like a YouTube guru. She kind of is one.

Make-up tutorials are big business. The biggest vloggers are reaching millions, collecting views at a speed that would dazzle the vast majority of everyday YouTubers who use the platform for more quotidian things. But regardless of the actual reach of each individual clip posted, there are rules that go into the production.