Theodore Gray is the author of the best-selling The Elements: A Visual Exploration of Every Known Atom in the Universe and Theo Gray's Mad Science: Experiments You Can Do at Home, but Probably Shouldn't, and of Popular Science magazine's "Gray Matter" column. He is the proprietor of periodictable.com. He is also cofounder of Wolfram Research, creators of the world's leading technical software system, Mathematica[registered], and Wolfram|Alpha[trademark]. With his company Touch Press, Gray is the developer of the best-selling iPad and iPhone e-book apps The Elements for iPad and Solar System for iPad. Nick Mann is a freelance photographer. Aside from having photographed more elements than probably anyone in the world, he is an accomplished landscape, sports, and event photographer.