For the uninitiated: The right side-up version of the cleavage-flaunting look is typically achieved with highly-cropped shirts or strategic placement of daring bras and bikini tops that expose bottom cleavage.
But the variant we're talking about here is believed to be first widely spread by Italian influencer Valentina Fradegrada, who has been upending tops and stuffing the ties into the front of the garment for the "official" upside down bikini Instagram page since 2018.
As the New York Post points out, Kylie Jenner has revived the titillating movement with yet another take involving an inverted triangular top that places the supportive ruching of the bathing suit atop of a woman's bust.
The top-earning model and makeup mogul recently debuted her upside-down underboob with a closeup of an electric blue two-piece (above). But it looks like stepsister and fellow influencer Kourtney Kardashian beat her to the punch in January.
For posterity's sake, the Post even dug up a nearly year-old snap of Kylie's supermodel sister Kendall rocking a Fradegrada-style inverted bikini.
And because any Kardashian-Jenner-related fashion trend is viewed by hundreds of millions of social media followers, the internet has already shared some thoughts: