Geuze is a type of Belgian lambic beer. It is made by blending young (1 year old) and old (2 to 3 year old) lambic beer, and immediately bottling. Young lambic contains sugar that has not yet fully fermented; old lambic contains active yeast that are hungry for sugars to ferment. This perfect combination sparks a secondary fermentation in the bottle, which gives us carbonation, as well as a full body and complex aroma.