The grape variety of wine represents the different varieties of vines on which the grapes grow. By choosing the grape variety of a particular wine, winegrowers, therefore, choose which types of grapes enter the production. Some wines are known as single-varietal (made from a single type of vine), while others are blends (made from different grape varieties). There are over 8,000 different types of grape varieties, some mostly local and others used in many different countries. It is possible to identify the different grape varieties by observing the appearance of the plant, the morphology of its leaves and buds, as well as the colors of the grapes. The science of grape varieties' studying is known as ampelography.