Procedure for making a Caffe Americano When making a Caffe Americano, does it matter whether you put the hot water or espresso in first?  This is not a complicated drink to make, but I've seen it prepared both ways.

If it does matter, why does the order affect the taste of the coffee?
Yes.  Adding water to Espresso is considered an Americano.  Doing it the other way around is called a Long Black.

According to that article and below sources, the Long Black preserves the crema, whereas the Americano preparation should not.  The manner in which the pour is done can contribute more to preserving or destroying the crema than the order.  An Americano should have no crema and the crema should be preserved in a Long Black.  It is the preservation or destruction of the crema that will affect the taste (and thus the pour) more than the order.