Last week, in a shopping center, I saw a teenager wearing jeans that were too low at the back to cover the upper part of his underpants. I thought to myself, “He looks ridiculous. Why does he want to do that? Why doesn’t he pull his trousers up?” Then I realized that the boy was wearing his trousers that way for exactly the same reason that I dyed my hair green when I was a teenager: It’s fashionable. “Old” people like me (I am 32) aren’t supposed to understand or to think it looks good. This fashion and the other youth fashions I saw in the shopping center are a language that young people speak that older people sometimes can’t learn. But I was interested and I wanted to find out more, so I asked my niece, Hannah, to help me. She’s 15, and she was my guide for my journey to find out more about teenage fashion.