Does Anybody Know How Fine (Specifically) The Ground Coffee For An Espresso Has To Be?

Q: I need this information for an industrial design project in college. Does anybody know how tiny the coffee needs to be for it to make a good Espresso?

A: There isnt a specified diameter, or measurement for grind size. At least one explanation for this is that each Espresso roast needs a different grind setting to account for differing moisture content, etc, etc. First of all, pleeaassse, do not call it coffee, because coffee and Espresso are 2 completely different things. Espresso beans are what you use to make an Espresso, okay? Anyways, they actually are not that fine, but they are very coarse. You can almost compare it to making a cup of coffee with a French Press. They must be very coarse so that they will pack in very tightly together when formed into a pod. When the pod is tightly packed, it will make a great Espresso, with just enough crema on top. Hope this helps!