The other day, when Chris and I were lunching at Sun Hong Kong restaurant, I aked for yao choy to be added to my lunch dish. I was told that there was only bok choy. Chris wondered what yao choy actually looked like, to which I responded that I'd take pictures of some yao choy next time I'm at Berkeley Bowl. Here are my thumbnails:
You can click on them to look for other sizes. For example: