And mark the fleers, the gibes, and notable scorns,
That dwell in every region of his face;
For I will make him tell the tale anew,
Where, how, how oft, how long ago, and when
He hath, and is again to cope your wife:
I say, but mark his gesture.
– William Shakespeare
Othello, Act 4, Scene 1. Iago sets out to play a cruel trick on Othello. Ordering Othello to hide, Iago says that he will engage Cassio and get him to talk about details of his sexual affair with Desdemona. Othello can then observe Cassio’s facial expressions, his sneers and scorns. Iago will be actually asking Cassio about Bianca, but Othello won’t hear what they are saying and will think they are talking about Desdemona. Iago is staging this event to inflame Othello’s jealousy.