Nipple crusader Scout Willis let it all hang out when she wore a totally sheer top to Rihanna's album cover unveiling party on Wednesday night.

Looks like Riri's album cover wasn't the only big reveal last night!

Demi Moore and Bruce Willis' 24-year-old daughter attended the bad gal's bash wearing sparkly pants underneath a sheer jumpsuit. Willis paired her odd outfit with copper heels. We don't know what to make of this look -- at all!

This isn't the first time we've seen Scout's nips. The celeb spawn has been all over Instagram in an attempt to #FreeTheNipple and even walked topless through the streets of NYC to promote the campaign.

While we have no problems with nipples -- we think the #FreeTheNipple is really a ridiculous campaign to get behind. Maybe put your energy on something that actually could help someone, like #FreeTheWronglyImprisoned or #HelpTheHomeless or #StopChildAbuse? Oh rich people problems!