A shoe is a type of footwear designed to keep the human foot safe and comfortable. Shoes can also be used for fashion and adornment. Shoes have evolved dramatically over time and from culture to culture, with shape and function initially being intricately linked. Fashion has also influenced numerous design components, such as whether or not shoes have very high heels or are flat. The style, complexity, and cost of contemporary footwear vary greatly. Simple sandals with simply a thin sole and a simple strap may be sold for a modest price. Famous designers' high-fashion shoes may be made of premium materials, have a complicated construction, and sell for a high price. Some shoes are created for specialised uses, such as climbing or skiing boots, while others have a broader application, such as sneakers, which have evolved from a single purpose sport shoe to a general purpose shoe. Shoes have traditionally been constructed of leather, wood, or canvas, but rubber, plastics, and other petrochemical-derived materials are increasingly being used.