Nori or flat seaweed sheets are the main ingredient in maki sushi or rolled-sushi. Nori is the most mild of all Japanese seaweed and is a good starter for people new to sea vegetables. Nori, also known as laver, is available in wafer-thin sheets, flakes (kizami nori) and strips. Due to the fact that sushi is rolled in nori, it has become the world's most popular seaweed.
Recently cheap Chinese nori has been introduced into the market. This nori is primarily grown in heavily industrialized areas of China in some of the most polluted waters in the world. Cheap nori is the last item to economize on; it may contain dangerously high levels of mercury and other heavy metals and other pollutants.