High-rise building
High-rise buildings became possible with the invention of the elevator (lift) and cheaper and more abundant building materials. The materials used for high-rise buildings are reinforced concrete and steel. Most North American style skyscrapers have a steel frame, while residential blocks are usually constructed of concrete.  There is no clear difference between a tower block and a skyscraper but a building with fifty or more stories is generally considered a skyscraper. The opposite of high-rise is a low-rise building and in the middle are mid-rise buildings.