Which one is the Teenager?

What's interesting is that I took the Sim I made as a young adult and then saved a copy to the library and then added them in as new Sim household members and then used styled looks and new hairstyles as I changed their ages.

I thought it was an interesting challenge because so many times I'll look at a Sim in the world and I'm like they will be my teens new friend only to find that they are actually a young adult or an adult.

I just really wish they had more defining features.