A penny for thoughts.
[Idiom] A PENNY FOR THOUGHTS. - Spark Curiosity and Engagement with Thought-Provoking Idioms
Ask someone what they are thinking about.
The idiom "a penny for your thoughts" is an invitation to share one's thoughts or to speak up when they seem preoccupied. It is a friendly, somewhat old-fashioned way to ask someone what is on their mind, often used to encourage a person to divulge their concerns or reflections.
Example Sentences
John looked distant at dinner; I said, "A penny for your thoughts?"
John seemed distracted at dinner, so I asked him what he was thinking.
"What are you thinking about? A penny for your thoughts," she asked.
She asked what he was thinking about.
He seemed so reflective that I couldn’t help but say, "A penny for your thoughts?"
He seemed so reflective that I wanted to know his thoughts.