On the practical side, microbes have been used in activities from biological warfare to fermentation in food processing; bread, beer and wine have been produced by yeasts from the dawn of civilisation, such as in ancient Egypt. Microorganisms such as bacteria and viruses are important as pathogens, causing disease to humans, crop plants, and domestic animals. Fermentation is an important source of chemicals, as industrial chemists discover how to manufacture a widening variety of organic chemicals including enzymes and bioactive molecules such as hormones and competitive inhibitors for use as medicines.