A cotyledon is part of the embryo within the seed of a plant. Often when the seed germinates, or begins to grow, the cotyledon may become the first leaves of the seedling. Botanists use the number of cotyledons present in the seed of a plant as a means of classification. Monocots are seeds that have only one cotyledon, while dicots are plants with two cotyledons. The cotyledons are formed during the process of embryogenesis along with the roots and shoots of the plant prior to germination.