COMMAND + F2 Yes I did that but still noticed some problems: Cable used: Thunderbolt. MacBook model: 15" Macbook Pro Retina Display. iMac Model : 27" Late 2012 Model, these thin ones! What I did: Connected them with thunderbolt, pressed Command+F2 on iMac's keyboard. Result: Yes I had the control of my MBP on my iMac display. Issue: I could NOT use Mouse or Keyboard of my iMac now. I still has to use MacBook's mouse and keyboard. Which is ridiculous! When I do the switch obviously I want the full control. I can't put MAcbook under my arms start typing on its keyboard and see the results on the iMAc display. Are these other things to do to fix this that I am not aware of ?