THAT'S exactly what the device manufactures WANT you to think. The don't want you to think in terms of a tightening effect would be a matter of contractile forces that shrink in all directions. That IMO explains why people think the devices THICKEN skin in one selective direction in a device that effects shrinkage in all directions which is what kicks up it's tightening effect.
I think a cross section of tissues/skin sample, if looked at under microscope, would not only reveal a layer of subcutaneous fat but also the matrix where there's a lot of stuff in there like collagen, elastin, glycoaminoglycans, some fat and so on. A matrix with a LOT of 'stuff' networked together. A matrix of older skin sample would differ from a younger one. We could say a younger matrix is plumper or 'juicier' and an older one is thinner or dried up.
Collagen is just one thing in a matrix with a LOT of inter-networked other things in it. 'Building new collagen' could mean destroying old collagen that's replaced with 'new collagen' where this new building arrangement is one of CONTRACTILE FORCES. Overall contractile forces are a SHRINKAGE effect and hence a TIGHTENING effect.
The device manufactures want people to think in terms of this tightening effect as a very positive thing. But don't want you thinking in terms of ; tightening = contractile forces = SHRINKAGE and shrinkage is in ALL DIRECTIONS where one of the directions would be in the THICKNESS direction.
A cross section of anything is going to have 3 dimensions: Length, width and thickness.
Originally Posted by: Greg 
Any thoughts on why fractional CO2 would make thin areas of skin worse? I had been thinking that laser treatments that stimulate collagen might somewhat thicken skin in areas where it's thin, like the neck; maybe that doesn't pan out.
It seems like neck skin, or a tissue layer beneath it, becomes more transparent with age such that the muscles/tendons beneath show through more--frustrating.
