We've had the thigh gap, the bikini bridge and the ridiculous A4 waist challenge, and now there's a new body-shaming trend to make us feel bad about ourselves - the ab crack.
An ab-crack is a curve that extends down the centre of the stomach and can only be achieved if you've spent lots of time at the gym.
Still confused? Here's a picture of Blurred Lines and Gone Girl star Emily Ratajkowski looking smoking hot in a bikini.
Butterfly Foundation CEO Christine Morgan says we should take these trends with a grain of salt, because they usually make us feel bad about ourselves.
"Viral social media trends such as this further promote body shaming and send out negative messages about body image," she said.
"Those who are unable to achieve the trend may feel like they don't measure up to the cultural ideals of beauty and body shape and can experience intense body dissatisfaction which is damaging to their psychological and physical wellbeing."
In other words, shake it off.