The term 'Seeing Thing' can be solved by the crossword solution 'EYE', which is a three letter word. The EYE is an organ of the body that is responsible for vision, allowing us to see the world around us. It is composed of several parts, including the cornea, iris, and pupil, which all work together to focus light onto the retina. The retina then converts the light into electrical signals that are sent to the brain, allowing us to interpret what we are seeing.