Mewing is a facial reconstructing technique that involves keeping your tongue on the roof of your mouth to change your jawlines shape. The idea behind mewing is that you can change the shape of your jawline if you think about the placement of your tongue in your mouth. The technique is named after Dr. Mike Mew, a British orthodontist, who promotes a form of orthodontics called “orthotropics” that focuses on “jaw posture” including retraining the position of the tongue.

Instructions for mewing vary, but the basics seem to be:

• Close your lips.
• Move your jaw so that your front bottom teeth are just behind your front upper teeth.
• Cover the roof of your mouth with your tongue.

Mewing is supposed to work by making your jawline more defined, which can help shape your face and perhaps make it look thinner, too. Some people also claim that it can help with sleep apnea, sinusitis, and other conditions. However, there is currently no scientific evidence to support the effectiveness of mewing. While not inherently dangerous, there’s not enough evidence to suggest that mewing is a reliable way to reshape your face or improve your health.