You know that sentimental longing you feel to return to your childhood? To flip on your favorite cartoon and munch on some Dunkaroos? That feeling is nostalgia — and its effects are very real. So real in fact, that we’re not alone in feeling them. According to Merriam-Webster, nostalgia is a wistful or excessively sentimental yearning about a past period or irrecoverable condition. Every 20 to 30 years, what was once popular when you were younger (8-13 years old) makes a reappearance in pop culture, especially in the form of movies, TV shows, or music.