The smell of childhood. Write about smells from your childhood, or smells from your alter ego’s childhood.
I immediately think of food: Fresh peaches, just picked strawberries with that earthy smell, piping hot chicken potpie fresh from the oven, just-baked chocolate chip cookies, hot buttery popcorn, s’mores = toasted marshmallows, melted chocolate, crisp graham crackers. Yum!
Outdoor smells: Freshly mown grass, river, diesel, ocean, fog, smog, campfire, burning leaves, snow.