Mewing is a facial reconstructing technique that involves keeping your tongue on the roof of your mouth to change your jawlines shape. The basic 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 involves flattening out your tongue against the roof of the mouth, with the lips touching and the teeth together. Supporters of the technique believe that over time, your tongue position will change your overall facial features, most notably the jawline. People also claim it can help with sleep apnea, sinusitis, and other conditions. However, there is no serious research that suggests mewing can change the shape of your jawline or help with other issues. Experts say it’s unlikely you’ll see any permanent change. Despite the hype, mewing has a lot of limitations and may not work like you might see on a YouTube video. If you have medical concerns about your mouth and jaw, you’re better off seeing a doctor for diagnosis and treatment.