Jennifer Lopez -- Good Genes Or Good Docs?

Jennifer Lopez's looks don't cost a thing.

Here’s a 26-year-old version of the Bronx triple threat at the premiere of her movie “My Family” in 1995 (left) and 21 years later ... the hot mama of two -- who turned 47 years old Sunday -- lettin’ her hair down at an L.A. party earlier this month (right).

Don't be fooled by the looks that she's got.

The question is ...