Stack

shows the current evaluation stack, giving a list of the tags associated with evaluations that are currently being done.

Stack[pattern]
gives a list of expressions currently being evaluated which match the pattern.

In the list returned by Stack[pattern], each expression is wrapped with HoldForm.

Print the stack where the Stack command is being evaluated:

Print the detailed stack contents including function arguments:

Print the stack where the Stack command is being evaluated:

Out[1]=

Print the detailed stack contents including function arguments:

Out[1]=

Use Stack inside of Dialog to see how it was reached:

Stack shows that the dialog from 2*Dialog[] is entered first:

Upon return from the first dialog, the other is entered: