the electric razor was the next big step. with electric razors, shaving cream, soap or water is no longer needed. electric razors use electricity to either make blades rotate or oscillate. that is the blades are either moved in circles, or they are moved up and down (or left and right). the razor is usually powered by a rechargeable battery. prof. alexandre horowitz invented the concept of rotating blades which is still marketed as "philishave" by philips.