Beer varieties can include ales, which are brewed using warm fermentation with a strain of brewer's yeast. Ales are typically fruity-tasting and full-bodied. They are usually darker in color than lagers, and have a higher alcohol content. Other beer varieties include lagers, stouts, porters, wheat beers, and lambics. Lagers are brewed using cold fermentation and bottom-fermenting yeast, resulting in a crisp, clean taste. Stouts and porters are dark, heavy beers that are made with roasted malt or barley, hops, water, and yeast. Wheat beers are brewed with a large proportion of wheat relative to the amount of malted barley used. Lambics are sour beers that are spontaneously fermented with wild yeasts.