The term 'organ of sight' is a reference to the EYE, which is a complex organ that allows us to see. The crossword solutions for this term are 'EYE' (3 letters) and 'EYEBALL' (7 letters). The EYE is composed of several parts, including the cornea, iris, pupil, lens, and retina. The EYEBALL is the round structure that contains the other parts of the EYE. It is filled with a clear gel-like substance called vitreous humor. The EYE is responsible for detecting light and converting it into electrical signals that are sent to the brain, allowing us to see.