Speaking of... 说起……
当对方讲起某个话题，而你对此感兴趣，就可以用"speaking of / talking of...（说起……，谈到……）"来接过话题。
1. Speaking of honesty, I know a lot of people who don't pay bus fares.
2. Speaking of Harry, have you seen him recently?
3. Talking of bicycles, China is called "The Kingdom of Bicycles".
A: I have some photos here taken by myself. Would you like to see them?
B: Sure. Speaking of photos, what type of film will be the best? You know, I'm planning a tour to Jiuzhaigou Valley.
A: I would get Fuji 200 film for taking photos of natural beauty.
B: Thank you so much. You're an expert.