Is Your Skin Healthy?

I don't know of anybody who doesn't want healthy skin, but how do you know when you have it? Sometimes it seems that judging skin health is almost "in the eye of the beholder." Or like good art, you know it when you see it.

In the past there weren't many medical studies that gave objective criteria on what makes skin appear healthy. However, lately, this has been a fairly hot topic, and now we have some good studies that reveal specific healthy skin characteristics.

Any idea what they are?