How does Iago plant the idea of Desdemona's infidelity in Othello's mind, and how does he make it grow? in act 3

Iago and Othello come upon Desdemona speaking to Cassio, and Cassio quickly takes his leave. This gave Iago the perfect opportunity to plant the idea in Othello's mind that his wife had been unfaithful. Once Iago plants the seeds of suspicion, Othello is easily baited.