What about Retin A cream for cellulite, stretch marks and skin elasticty and thickness - how is it used?

Having performed bench research with retinoids including all-trans retinoic acid (Retin-A), I can tell you that retinoids have wonderful effects on the health and therefore the beauty of the skin.  They increase fibroblasts' production of collagen, especially type 1, elastin, and other structural proteins that are responsible for thickness, elasticity, and strength of the skin.  They also redistribute melanin, which helps with discoloration and tone, and correct precancerous growths. Some subclinical skin cancers have resolved in experimental trials as well.Retin-A, and Retinol 1% have been proven to have these effects. Tazarac and Avage are even more potent in these regards. Differin does not have all of these benefits.Clark, SD., Kobayashi, DK., and Welgus, HG.: “Regulations of the expression of tissue
inhibitorof metalloproteinases and collagenase by retinoids and glucocortiods in human
fibroblasts.” Journal of Clinical Investigations, 80 (5): 1280-1288, 1987

Retin A will not help for stretch marks or cellulite.  It will help with the fine lines around the eyes.