The extreme close up is incredibly important. When you’re telling any story, there are small details you need to emphasise for your audience. Your character receives a text message? Show an extreme close up of their phone. Your character receives an important letter? Capture an extreme close up of the words on the page.
In Saving Private Ryan (1998), director Steven Spielberg ends the opening scene with an extreme close up of a veteran’s eyes as he recalls the events of World War II. In the next scene, a similar extreme close up of a young Captain Miller (Tom Hanks) suggests that he is the veteran from the opening scene.
In Psycho (1960), Alfred Hitchcock uses a number of extreme close ups, notably the extreme close up of Norman Bate’s eye looking through the peep hole in his parlour.
Need to emphasise something? Get the camera nice and close and use an extreme close up!