Seaweeds are now used as multifunctional foods in many parts of the world. Seaweeds are considered as functional foods because of the presence of high amounts of minerals and vitamins as well as some beneficial bioactive compounds in them. A functional food produces a beneficial effect in human body by increasing the welfare and decreasing the risk of diseases. When it comes to the matter of health, prevention is better than cure and functional foods are preventative than curative. Major seaweeds that are explained in this book are agar seaweeds, winged kelp, irish moss, purple laver or nori, green laver, kombu, dulse, caulerpa, spirulina and wakame.