The International Thermonuclear Experimental Reactor,or ITER,is one of the world's biggest and most costly research projects. Its aim,generating energy from nuclear fusion,is almost as lofty as ITER's 10 billion euro price.With construction on the reactor,also known as a TOKAMAK,scheduled to begin this year in Cadarache,France,Tomorrow-Today surveys the history of scientists' quest to recreate the way the sun makes energy and harness it for earthly uses.