To celebrate Scientific American ’s 180th anniversary, we’re publishing jigsaw puzzles to show off some of our most ...

It is enamel. Like hair and nails, this hard substance is made by epithelial cells. Once it was thought to be as inert as rock; now it is known to exchange its substance with the body fluids ...

The input-output system of a computer consists of the programs and devices that allow the machine and its user to communicate. Recently graphical devices for this purpose have evolved rapidly ...