title_body: Pouring espresso into hot water versus hot water into espresso
upvoted_answer: I would suspect that a few centigrades make all the difference here. With coffee, too high temperatures will negatively affect your flavor. Rule of thumb: Hot is good, boiling isn’t.
  
  If you put the water in your mug first, you’ll lose just a bit of temperature as the water warms the mug and/or stands for a bit until you add the coffee. 
  
  If you reverse the order, you are effectively scalding (some of) the coffee with the boiling water, losing volatile aromatic compounds and degrading others.