When President Fidel Castro, on the eve of his 75th birthday, handed a Cuban flag to the head of the Communist youth organization, it was more than a ceremonial move.

Castro was metaphorically enacting what he calls his most powerful dream -- that Cuba's younger generations take over from him once he's gone to keep his revolution alive. Castro marks his 75th birthday Monday. His voice is no longer as fiery as it once was, and his beard is not as thick as when he and his allies overthrew Cuban dictator Fulgencio Batista in 1959. But he continues to show impressive stamina, still speaking for four or five hours non-stop and still getting by on only a few hours of sleep. His regime has survived the collapse of his longtime Soviet patrons and four decades of official U.S. hostility, including an attempt by American-armed Cuban exiles to overthrow him in 1961 and an economic embargo that has persisted through nine U.S. administrations. Many opponents of Castro's government argue that democratic change is inevitable -- and that it should be led by Castro himself to avoid a power vacuum and the kind of social turmoil that occurred in the former Soviet republics. Castro and his designated successor, younger brother Raul Castro, laugh off the suggestion that communism in Cuba is destined to collapse.