“We need oxygen every moment, so correct breathing is critical for the development of the face, mouth, and teeth,” says Dr. Kami Hoss, dentist, board member at the UCLA School of Dentistry, and author of If Your Mouth Could Talk. He notes that you should be breathing through your nose, and your tongue should be gently resting on the roof of your mouth against the palate right behind your teeth. And your tongue plays a key role in the development of your face. “The whole mouth grows around your tongue, so it’s very critical for children [to breathe properly] because it really impacts their growth and development,” says Hoss.