But up to now the abs as status symbol were mostly the preserve of the Action Man-inspired male (please see "cosmetic abdominal etching" for full details).
That's until the female "ab crack" arrived on the scene - a groove of muscle from between the ribs down to the belly button in a sort of direct extension of the cleavage.
It's the result of working the "core" so much that muscle builds down both the left- and right-hand side of the lower abdomen.
That's the science.
But now the "ab crack" is being shared on Instagram as the hottest standard for female body perfection, with many holding up Emily Ratajkowski as a perfect example of the standard a woman should aim for. Unless you're an internet troll - they take a slightly different view:
Indy100 wouldn't like to take sides, but we do quite like this chap's view: