Water

• Obvious though it sounds, water is an essential ingredient. Good-quality tap water is normally all that is required, though for homebrewing purposes you may wish to boil it before use, as this can help eliminate any chemical aftertastes.
  
  

Malt

• The malting process begins with barley being soaked in water until the seeds germinate. This process converts the grains starches into the sugars required in the brewing process. Further germination is then stopped by drying the barley with hot air. The next process, called mashing, soaks the cracked barley in hot water to convert as much of the remaining starch into sugars. The resulting liquid, called wort, is then concentrated to form the thick, dark malt extract familiar to homebrew enthusiasts.
  
  

Hops

• Hops are the flowering clusters of the perennial climbing plant, Humulus lupulus. The flowers contain various bitter resins and essential oils that both add flavor to beer and help stabilize it, thus extending its shelf life. Hops have been cultivated for over 1,000 years and the different available varieties impart subtly different flavors to the finished beer.
  
  

Yeast

• Yeast is a microscopic fungal organism that is the essential living ingredient in beer. In the fermentation process, yeast consumes the sugars and in turn creates alcohol and carbon dioxide. It is this process that turns what is initially just a mixture of ingredients into beer. Different strains of yeast are widely available, each with their own qualities. Some ferment at the top of the liquid, others at the bottom, while some can tolerate higher concentrations of alcohol than others before they die. The choice of yeast can therefore significantly change the flavor and qualities of the finished beer.