Caffè Americano or simply Americano is prepared by adding hot water to espresso, giving a similar strength, but different flavor from regular drip coffee. The strength of an Americano varies with the number of shots of espresso added. Variations include the Long Black, Lungo and Red eye.
To achieve a Double Americano, use a double-shot of Espresso. You can also prepare the Americano by adding as much water as you like, which will create different strengths and, in turn, tastes (less water = more intensive; and vise versa).
The first Americano coffee is known to have come from the battlefield of World War II. American GI's in Europe tried to make a coffee similar to the one they were accustomed to by diluting it with hot water. Later on the coffee became popular in the US.