Today, thousands of different types of shoes exist in our world and just as many engineers are working to develop new styles and improve existing designs. Engineers consider many variables when designing shoes—material type for durability and function, anticipated shoe stresses and strains, the health and safety of the shoe wearer, and the shoe's aesthetics. Engineers often work with podiatrists to design high-tech shoes that are safe, comfortable and stylish! Mechanical engineers apply principles of physics to analyze, design and manufacture mechanical systems, including new shoes. Materials engineers—specialists in the structure of materials and their properties—select and design the best combinations of materials for specific shoe purposes.