What is seed made up of?
Main parts are:

Chaff : a seed, just harvested, is covered with a yellowish or brownish color multi-layers cod, called chaff.
It forms 20% of the whole wheight.

Husk: it is a layer, under the chaff, rich in nutritive elements and proteins.

Endosperm : it is a layer, also called albumen, rich in vitamins and starch.

Embryo ( or germ ): Each grain has an embryo.
It will start a new rice plant, so it is a very important part of the grain.