iMOL3Dview allows you to view the molecules in things like DNA, Allcin, and caffeine. iMOL3Dview for the iPhone, iPod Touch, and iPad includes almost all the genetic molecules you would ever want to see. these iMOL3Dview app provides many 3D features including rotating model with finger movement, zooming in/out, changing color, etc.
Theres also a Color Key that allows you to identify the different elements that make up the molecule. In addition, you have the option of seeing the molecule as a ball-and-stick image or with space filling.