The seed, or matured ovule is made up of three parts. The embryo is a miniature plant in an arrested state of development. Most seeds contain a built-in food supply called the endosperm (orchid are an exception). The endosperm can be made up of proteins, carbohydrates or fats. The third part a hard outer covering called a seed coat. It protects the seed from disease and insects, and prevents water from entering the seed which would initiate the germination process before the proper time.