It is believed that for the first time fish and rice were connected with each other in Japan in 6 century AD. That was made in case to prevent fish from spoiling. Fish was tightly surrounded with rice and placed in barrels with salt for weeks.
In the end of 17th century people learned to cook rice vinegar which perfectly combined with rice. And with this new dish raw fish and seafood were served.
A lot of fish such as tuna, eel and salmon are used for sushi. Seafood is also popular in this dish: squid, octopus, shrimp, mussels and others. Because of these products sushi is a very helpful food for health.
Sushi is a difficult science. Some courses of sushi masters are lasting up to 3 years. But it is very easy to enjoy this dish even at home. You just need to have right fresh products.