When he held my hand. It’s a pretty small thing but after getting to know each other we went on a date and while we were walking around he held my hand, weird to say but no man had ever done that in a tender non sexual way before (only ever had girlfriends and one night stands with guys) and I normally HATE my personal space being encroached, but as soon as he held my hand I felt like never letting him go. Now three years in an amazing relationship and counting.