Eggs are graded by the U.S. Department of Agriculture (USDA) or a state agency following USDA guidelines. Grades AA, A or B are given based upon the interior and exterior quality, not the size of the egg. Criteria include the appearance of the shell, how the egg spreads when it is cracked open, the appearance of the albumen and yolk, and the overall usability (e.g., any use (Grades AA and A), including frying, poaching and cooking in the shell, versus restriction to baking and scrambling, for Grade B eggs which have slightly abnormal shapes or stained shells). The grade does not define the nutritional value of the egg.