How Does Tretinoin Work to Reduce Fine Lines?

I've been using tretinoin 0.025% for about 2 months. Had no peeling, swelling, redness... Recently (about 5 days ago) I switched to 0.050% and then I started to see some peeling. Still no redness or visible swelling. What i've noticed is that some fine lines just look better today. They are still there, but just look plumpler and less visible.

I can't understand how this happened. Is it because of imperceptible swelling (microscopic)? Does tretinoin work on the basis of constant swelling? If so, would constant swelling from tretinoin cause damage to the skin on the long run?