"I believe that the best kid's faces are from kids who are allowed to run outside and play, who are served a healthy diet and don't spend a ton of time on screens."  - Dark Indigo

The science behind this statement:

Exercise builds airway from inside-out.  It may also help to combat mouth breathing.  That is because oxygen utilization is up.  And because our bodies are designed to adapt.  An adaptation is with pressure.  Even light pressure from air.  If we exercise with out mouths closed (moderate - not overdoing)… then that can help.  Overdoing exercise (especially in cold/dry climates) can cause airway injury.  This is where the airway starts to constrict.  It's as if our bodies are saying, "ENOUGH ALREADY" and keep us from overexerting.  That's why I say "allowed to" and not "forced to".
Sunlight has vitamin D (which you can't get behind glass.. because UVB is blocked by glass).  This hormone building block is NOT a vitamin.  It is necessary for bone growth and development.  I don't force a kid to go outside in the winter.  The air is too dry.  I also know that vitamin D really isn't being created during certain times of the year.  That's why I don't force a kid outside.. they'll likely just injure their airway or be cold or what-not.  Natural, people.  Natural.  That's the whole friggen point.  Vitamin D is made in the summer.  Read more of Stasha Gominak on this.  A healthy diet can help to develop good arches.  A crunchy diet will shorted the face whereas a softer diet lengthens it (that's why braces lengthen the face... not because they actually do... but because of no carrots, ice, hard candies, etc.  You can counter that by having shoestring carrots, etc.).  The thing is, though, that a few carrots and apples with shorten the face, but you can also overshorten it.  It is dangerous to overshorten and to shorten without widening... because then the palatal vault gets more into the precious cargo nasal area.  That is why a healthy diet of things like melons and stuff can WIDEN.. not just shorten.  That is my suspicion, though it hasn't been tested.  Tested that carrots shorten the face.  Chewing lengthens arches.  That is more for arch growth, but not the placement of that arch growth.  Tongue is more for widening.  Having a better tongue placement or stronger tongue through food, I believe, is good for creating width.  Not tested, though.  Here's what has been tested... chewing gum 1 hr. day as Dr. Mew's daughter was forced to is damaging.  That's why we don't hear about it.  That's why I say "served a healthy diet" not forced to eat a healthy diet.

Screen time creates bad posture.  A forward head posture means that the airway isn't being used properly.  It is forward, which is a more open-airway posture.  When a kid is growing, you can remarkably change their airway.  That is because everything is growing.  So... basically, posture is important in kids... probably moreso than adults.  However, I don't harp of them too much... just if excessive.