1. Whole grains: unprocessed grains that retain all three parts of the grain kernel (bran, germ, and endosperm). Example: brown rice 2. Refined grains: grains that have been processed to remove the bran and germ, leaving only the endosperm. Example: white bread 3. Ancient grains: grains that have been cultivated for centuries and have not been significantly altered by modern breeding practices. Example: quinoa