Think of all the different kinds of things you interact with everyday, then consider all the different kinds of materials from which they are made: plastic, metal, cotton, wood, glass, ceramics, synthetic fabric, paper, leather, etc.
Engineers not only design things based on available materials, they develop new materials that pave the way to better, safer, more effective products.
They work closely with scientists and other researchers to scale experimental methods that produce a small amount of a material in a lab into manufacturing processes that produce huge quantities that can go into making the things we buy.