Miley Cyrus celebrated her 18th birthday by experimenting with a bong and catching a case of the giggles but sources say she was not smoking marijuana.
The video was shot during a party at Miley's L.A. area home 5 days after her 18th birthday.
According to a source connected with Miley ... the smoke filling the bong is a natural herb called salvia which has psychedelic qualities. Possession of salvia is legal in California.
CLICK HERE to watch the video of Miley smoking.