The black seaweed wrappers used in makimono are called nori. Nori is a type of algae, traditionally cultivated in the harbors of Japan. Originally, algae was scraped from dock pilings, rolled out into thin, edible sheets, and dried in the sun, in a process similar to making rice paper. Today, the commercial product is farmed, processed, toasted, packaged, and sold in sheets.
The size of a nori sheet influences the size of makimono. A full-size sheet produces futomaki, and a half produces hosomaki and temaki. To produce gunkan and some other makimono, an appropriately-sized piece of nori is cut from a whole sheet.
Nori by itself is an edible snack and is available with salt or flavored with teriyaki sauce.
Source: http://en.wikipedia.org/wiki/Sushi; April 19, 2014
Tobiko is the Japanese word for the flying fish roe. It is most widely known for its use in creating certain types of sushi.
The eggs are small, ranging from 0.5 mm - 0.8 mm. For comparison, tobiko is larger than masago, (capelin roe), but smaller than ikura, (salmon roe). Natural tobiko has a red-orange color, a mild smoky or salty taste, and a crunchy texture.
Sometimes tobiko is colored to change its appearance, other natural ingredients are used to accomplish the change, such as, squid ink to make it black, yuzu to make it pale orange (almost yellow), or even wasabi to make it green and spicy. Sometimes a serving of tobiko contains several pieces, each having a different color.
When prepared as sashimi it may be presented on avocado halves or wedges. Tobiko is used in the creation of many other Japanese dishes. Often, Tobiko is used as an ingredient in California rolls.
Frequently masago, capelin or smelt roe, is substituted for tobiko, due to its similar appearance and flavor. The tiny size of the individual eggs is apparent to the experienced diner, however.
The raw roe is very nutritious, due to its high vitamin content, high protein content, and large ratio of omega-3 to omega-6 fatty acids. Although it contains a large amount of cholesterol, the amount of roe consumed in typical servings, about a tablespoon, does not create an issue in a healthy diet since it amounts to approximately seventeen percent of the recommended daily value for cholesterol.