Peruse the aisles of any Japanese grocery store and you’ll find an astonishing array of seaweeds. Each has its own purpose and method of preparation. Here’s a look at a few of the most common types:1. KOMBU This thick kelp has a dusting of white powder that accounts for much of its salty flavor; don’t rinse it off. Wipe kombu with a damp cloth, soak in cold water, and refrigerate overnight. Use as is for stock (dashi), or add to soups. 2. NORI The sushi-roll seaweed, nori is made from algae dried in thin layers. To make it pliable, hold with tongs six inches above a flame until it turns bright green. 3. HIJIKI Popular in hijiki mame—hijiki and soybeans sautéed in oil with soy sauce and sugar. It has an assertive sea flavor. Soak in warm water for 20 minutes. 4. WAKAME Served as a snack or as a garnish for soups and salads, wakame has a delicate taste. Soak in tepid water for 15 minutes.