The term 'eye opening' can be broken down into four crossword solutions: REMARKABLE (10 letters), PUPIL (5 letters), opti (4 letters), and SLIT (4 letters). REMARKABLE refers to something that is extraordinary or noteworthy, and is often used to describe an event or experience that is particularly eye-opening. The PUPIL is the black circle in the center of the eye that allows light to enter the eye. Opti is short for optical, which relates to vision and sight. Finally, a SLIT is a narrow opening, which is often associated with the eye in terms of the shape of the PUPIL. All of these words together create a phrase that describes something that is particularly insightful or revealing.