In a term coined by Romanian historian of religions Mircea Eliade (meer-CHAY-uh ell-YAH-dih), a hierophany is an eruption of the sacred into the realm of the profane (i.e., the ordinary, not the vulgar/obscene). One suddenly finds oneself standing in the presence of the holy, a fact that disrupts the normal, mundane continuity of human existence.
I'm fascinated by theistic fiction, i.e., fiction about the presence of the holy in our midst. A great example of this sort of fiction is the short story titled "The Visitation," by sci-fi author Greg Bear. You can read a truncated version of the story for yourself here.