(Tretinoin Gel 0.1%)
Retin-A Micro was approved by the U.S. Food and Drug Administration on February 7, 1997 for the treatment of acne vulgaris. What makes Retin-A Micro unique is the Microsponge® systems technology. The Microsponge® system prevents the accumulation of excessive medication within the surface layers of the skin. It’s pretty neat, actually:  each Microsponge® is less than one-thousandth of an inch in diameter, holding a small amount of tretinoin in reserve and introducing only small amounts of tretinoin to the skin over time. The Microsponge® is believed to be the reason why Retin-A Micro has higher efficacy and lower irritation rates than Retin-A. By contrast, other forms of retinoids may release active ingredients as soon as they are applied, producing a highly-concentrated layer that should absorb into the skin quickly, but which can accumulate in the skin over time. It’s my favorite for acne!
https://www.futurederm.com/know-your-prescription-retinoids-the-differences-between-retin-a-retin-a-micro-renova-differin-and-tazorac/