There are two main criteria for classifying caviar: the dimension and the color of the eggs. The bigger and the lighter they are, the more prized they are. For example the most valuable caviar, the famous Beluga caviar, has eggs with diameter larger than 3 mm and the color of the egg is between light gray and dark gray. Other kinds of caviar are generally darker and with a thiner diameter, so they are cheaper than Beluga caviar.