For centuries, beer has been made with four basic ingredients: malt, water, hops, and yeast. Put basically, the sugars are extracted from grains so that yeast can convert it to alcohol and carbon dioxide, creating the final product: beer. While craft brewing is certainly guided by scientific principles, there is creativity involved, as brewers need to vary the combinations of grains, hops, yeast, and extracts to create a multitude of styles. This dedication to creativity is what sets craft beer apart from mass market produced beer. The major domestic beer companies use cheaper ingredients - for instance, rice or corn instead of hops - to reduce the price of the final product, creating a watery, bland product.