From the academic point of view there are only two kinds of beer, namely, beer made solely of barley malt and hops, and beer made from substitutes for barley, the hops being a common content of both classes. Another classification of beers is lager beer as distinguished from other beers. Lager beers are those beers which are kept for a considerable time in the cellars for ripening, as distinguished from beer, which in this case means a product which has no very great age. Those new beers are sometimes called "steam beers."