Answer:
''The eyes are the window to the soul'' means that a person's eyes can reveal a lot about their inner feelings or emotions. For example, by looking into someone's eyes, you'll be able to know if they are feeling sad even though they might be smiling.
The origin of this expression is unknown, but there are similar ideas found in ancient Latin proverbs and biblical texts. For example, a related Latin expression is found in Cicero's Orator, which translates as 'The face is a picture of the mind as the eyes are its interpreter.'