Cement is a substance that can bind other materials together. It is made by heating limestone with clay and plaster (calcium, silicon, iron, and aluminum) and in some cases Pozzolanic ashes.
The Assyrians and Babylonians used clay for this purpose, and the Egyptians advanced to the discovery of lime and gypsum mortar as a binding agent for building such structures as the Pyramids. The Greeks made further improvements and finally the Romans developed a cement that produced structures of remarkable durability. 
In 1824 the English mason Joseph Aspdin registered a patent on a cement that he called Portland Cement.
Cement has become one of the primary building materials for buildings such as skyscrapers.