Factory tours? (Shenzhen)

Hello,

My wife and I are about to come to China to live for 3+ months this year. We are planning to come through Hong Kong, and so we thought we would pass through Shenzhen on the way into the mainland.

We're very interested in factories and seeing things made / processed / assembled (food, manufacturing, anything). I wanted to know if anyone had experience arranging factory visits or had advice on how to go about it. We are just on tourist visas and we're not journalists. We're just curious folks.

Thanks!
Matt