What jadasc said. You pour about a shot of absinthe into a tall glass, and put an "absinthe spoon" on top of the glass (which is a sort of slotted spoon), and put a sugar cube on the spoon, and pour water over the sugar cube slowly, until the sugar dissolves and the glass is full. It's about one part absinthe to three or four parts water, and the absinthe turns from green to milky-yellowish-greenish-white. It's nifty.