Hey everyone, I have been searching for this answer and I realized that I don't even really know what to search for. Here's what I'm trying to do, and maybe someone can give me at least what to search for, if not the answer itself! I'm building a Cocoa app right now in which I want to be able to click any window that is open and get the process serial or any kind of window ID number that I can compare to other windows. This is similar to the functionality of the Grab screen-shot utility that comes with OS X. If you open Grab, then select Capture->Window, it comes up with a message box and you click "Choose Window", and the cursor becomes a camera, and any window you click while it is a camera is what Grab takes the screenshot of. I want to be able to click a window and return its ID. Any thoughts?? Any and all help is greatly appreciated!