Mewing does nothing, it's a scam that has convinced a lot of retards.
All the photos of 'face changes' are looksmaxxers finishing puberty, losing weight, or physically altering their appearance (sucking cheeks, lowering the bottom mandible, etc.)
There is no evidence that mewing works, there are health risks associated with mewing (disfiguring teeth and possibly 'TMJ' as the looksmaxxers call it) and the premise isn't even logical or intuitive.
The most ardent mewing supporters claim it takes years with little difference, because they can't admit it does nothing.