Early humans realized that for some uses, combinations of materials often produced properties in the mixed material, or composite , that were superior to those of the component materials themselves. For example, mud bricks were reinforced with straw in ancient Egypt, and the warriors of ancient Damascus layered iron and steel in their swords. This represented significant advances in buildings and weapons, respectively, and led to the temporary supremacy of the inventing culture. The advantages of such composite materials and structures have not faded with the passage of time but have grown in use and sophistication. For example, aggregate-reinforced concrete, a simple composite, resulted in improved performance compared to cement, and then steel-reinforced concrete, a more complex composite, resulted in even greater improvements in performance in what is surely the most widely used of all engineering materials. Now, nano-scale 1 particles are leading to unimagined improvements in the properties of ceramics, metals, and polymers of all kinds, and nanotechnology is only in its embryonic state.