A espresso serving size that is usually measured in shots, which are between 25 and 30 ml (around 1 fluid ounce) in size.

espresso also to becoming the base for other drinks, such as lattes, cappuccini, macchiato.

espresso contains approximately three times the caffeine content of regular brewed coffee (1.700 g/l (50 mg per fluid ounce) of espresso versus 0.50-0.75 g/l (14-22 mg per ounce) for brewed coffee). Compared on the basis of usual serving sizes, a 30 ml (1 fluid ounce) shot of espresso has about half the caffeine of a standard 180 ml (6 fluid ounce) cup of American-style coffee, which varies from 80 to 130 mg.

besides starbucks and coffee bean, u can try Illy coffee!