Vision is simple. We open our eyes and, instantly, the world surrounding us is perceived in all its splendor. Yet Artificial Intelligence has been trying with very limited success for over 20 years to endow machines with similar abilities. A large van, filled with computers and driving unguided at a mile per hour across gently sloping hills in Colorado and using a laser-range system to “see” is the most we have accomplished so far. On the other hand, computers can play a decent game of chess or prove simple mathematical theorems. It is ironic that we are unable to reproduce perceptual abilities which we share with most animals while some of the features distinguishing us from even our closest cousins, chimpanzees, can be carried out by machines. Vision is difficult.