When does mercutio mention queen mab?

In William Shakespeare's play Romeo and Juliet, Mercutio mentions Queen Mab in Act 1, Scene 4. Mercutio's famous speech about Queen Mab occurs during a conversation with Romeo and Benvolio about dreams. Mercutio describes Queen Mab as a tiny fairy who rides in a nutshell chariot drawn by a team of atoms and enters people's minds to inspire dreams. Through this speech, Mercutio explores the relationship between imagination and reality.