As with most crops, there are also different varieties of grapevine, which in viticulture are known as vine varieties (cultivars). The morphological description can be found under the keyword vine. The science of describing grape varieties is called ampelography (grape variety science). The botanical taxonomy (hierarchical systematics based on kinship) is described under vine systematics. Over thousands of years, thousands of new grape varieties have been created by spontaneous (natural) crossing and sowing, random mutations and, above all, from the 19th century onwards, also by targeted new breeding. They are always primarily the result of fertilised seeds or targeted seed sowing, i.e. they are the products of generative (sexual) reproduction.