An americano is simply just hot water and espresso. It’ll either be served 1/2 and 1/2 or 1/3 espresso to 2/3 water, depending on the coffee shop in question or how you’ve chosen to brew it. There is debate about which should be added first, but in the case of the americano,
espresso should always be added first as the crema mixes in and creates a more mellow, even taste.