Seeing a smile from Young Man with Autism

I have been working with a young adult with autism in Mountain Home Idaho recently.  His attention span is short, and his interactions with me have been short too.  He will interact for a few minutes at a time.  But everytime I go he interacts a little bit more.  The last time I worked with him I saw something amazing.  He was more interactive with me than he has ever been.  He was playing music in time, following simple directions in the songs and even singing with me.  But my favorite moment was when he looked at me and gave me a big smile.  I had never seen him smile before, and it was a beautiful smile and a beautiful moment I won't forget.