there are 15 epochs in the game, each representing a part of history. as the player advances through the epochs, new and improved units and structures become available. some of the epochs in "empire earth ii" are identical to their counterparts in the original "empire earth"—one exception is that "empire earth ii" does not allow players to expand their empires into space. the epochs are the stone age, copper age, bronze age, iron age, dark ages, middle ages, renaissance, imperial age, enlightenment age, industrial age, modern age, atomic age, digital age, genetic age and synthetic age.