Using iMac 21.5 mid 2010 as an external monitor of Macbook Pro Retina late 2013 15"? Can I connect iMac 21.5 mid 2010 as an external monitor of Macbook Pro Retina late 2013 15"? How can I connect them?

I read some articles that say it can be done with Mini DisplayPort-to-Mini DisplayPort like http://www.macobserver.com/tmo/article/connect-a-macbook-to-an-imacs-display-with-target-display-mode but I’m not sure if the author is referring to the 27 iMac only or all iMacs mid 2010.

Has anybody had some experience in connecting these?

Here’s my iMac details:
I've tried this and yes it does/can work, depending on your setup. So far I've managed to hook a 2012 MBP 13" to a 2012 21" iMac via Thunderbolt, and the cmd + F2 function works once logged in.

However, I've not managed to connect to a 2011 iMac (non-Thunderbolt model) using the same MacBook and Thunderbolt cable - I don't have a DisplayPort cable to hand to see if that works or not so right now I can't verify if yours will work or not.