It's an act of solidarity.
If you've been scrolling through Twitter over the last few days you may have seen a few granny pants.
While you may have just thought it was just some social media users love of oversharing, but the pictures are actually pretty inspiring.
https://twitter.com/sam_armytage/status/763121433094426624
Sam Armytage is a TV news presenter who works in Australia on Sunrise.
The movement all began when the Daily Mail in Australia posted a 'news story' about Sam.
The caption read: ''Sam Armytage's giant granny panties show a visible line''
https://twitter.com/DailyMailAU/status/807891586797436928
Yes, this is sadly a real tweet.
So rather than tweet back to the Daily Mail to rant about the ridiculousness of the whole thing, and rather than ignore it completely, women have been showing solidarity.
https://twitter.com/DianaDJ7/status/808170308028903424
Women all over Twitter began proudly posting images of their large, comfortable knickers to banish the apparent stigma the writers at the Mail seem to have about granny pants.
https://twitter.com/CountessHobart/status/808205030100611074
https://twitter.com/RubySaysSo/status/808289868639965186
https://twitter.com/MaddalenaGalli/status/808250758772625408
https://twitter.com/Moonbirdsunbird/status/808279761260687360
https://twitter.com/dakkas84/status/808473712475271170
And our personal favourite:
https://twitter.com/L_Day/status/808442428998893570
Ladies and gentlemen, wear whatever the hell you want.