People keep asking how to move everyone in one circle to another (so you can have Venn-diagram-like relationships). You can't actually put one circle into another so that they keep that relationship, but if you go to your circles, click on the name of one, and click "View circle in tab", the members of the circle will show up above your circles. Then "More actions → Select all", or just select a few. Then you can drag and drop to other circles all you want.

(There's no restriction against putting people in as many circles as you want. I wonder why so many people have that perception? Thinking they're categorizing or putting something in a folder? Remember, folks, this is the company that gave your email labels. :-)

Update: +Robin Millette points out that I responded to requests to move people from one circle to another with instructions on how to copy them. I've addressed this further in this post: https://plus.google.com/116222833568410151476/posts/SeCMDyYNzsa
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