Today's phrase is "read someone's mind."
This means that you know what someone is thinking (usually because you know the person well).
A. Your father is thinking about work.
B. How do you know?
A. After 35 years of marriage, I can read his mind .
I didn't tell her that I was unhappy. She just knew. She must have read my mind.
I'm sorry, but I can't read your mind. Where do you want to go for dinner?