Innovations continued through the Middle Ages with innovations such as silk, the horse collar and horseshoes in the first few hundred years after the fall of the Roman Empire. Medieval technology saw the use of simple machines (such as the lever, the screw, and the pulley) being combined to form more complicated tools, such as the wheelbarrow, windmills and clocks. The Renaissance brought forth many of these innovations, including the printing press (which facilitated the greater communication of knowledge), and technology became increasingly associated with science, beginning a cycle of mutual advancement. The advancements in technology in this era allowed a more steady supply of food, followed by the wider availability of consumer goods. Starting in the United Kingdom in the 18th century, the Industrial Revolution was a period of great technological discovery, particularly in the areas of agriculture, manufacturing, mining, metallurgy, and transport, driven by the discovery of steam power. Technology took another step in a second industrial revolution with the harnessing of electricity to create such innovations as the electric motor, light bulb, and countless others. Scientific advancement and the discovery of new concepts later allowed for powered flight and advancements in medicine, chemistry, physics, and engineering. The rise in technology has led to skyscrapers and broad urban areas whose inhabitants rely on motors to transport them and their food supply. Communication was also greatly improved with the invention of the telegraph, telephone, radio and television. The late 19th and early 20th centuries saw a revolution in transportation with the invention of the airplane and automobile.