Emma Watson has grown up from the Hermione Granger of the Harry Potter series and taken a bold step by posing nude in front of camera. The 22-year-old actress bares all for James Houston's Natural Beauty book, benefiting Global Green USA.

In one of the pictures, she is seen completely drenched and is holding an orchid in one hand with her eyes closed.

"My friend is supporting GlobalGreenUSA with his book Natural Beauty. It's out now. : ) X" she wrote on her Twitter account, along with a picture.

Other leading models and celebrities who will be featured in the 120-page-book include Christy Turlington, Adrian Grenier, Brooke Shields, Elle Macpherson, Karlie Kloss, Arizona Muse and Anja Rubik.

"This project merges my longtime interest in the human form and my passion for the natural world," Houston said, "Natural Beauty was created to celebrate the beauty of nature, emphasizing what we still have versus what we have lost. I hope to raise environmental awareness among the younger audience through this project."

The project's 12-part web series is set to be launched on 25 March, and the book can be pre-ordered on Amazon's website.

The Perks of Being a Wallflower actress recently shot down rumours that she will play the role of Anastasia Steele in the film version of EL James's best-selling book, Fifty Shades of Grey.

"Who here actually thinks I would do 50 Shades of Grey as a movie? Like really. For real. In real life," she tweeted.

Finally, Watson will be soon seen in Sofia Coppola-directed film The Bling Ring, based on true events that revolve around a group of teenagers who steal off celebrity homes such as Orlando Bloom, Rachel Bilson and Paris Hilton. The movie will hit theatres by 14 June.

Take a look at the behind-the-scene video of Natural Beauty below...