Below, you can see the preview of the Unix History (move on the white zone to get a bigger image):

This is a simplified diagram of unix history. There are numerous derivative systems not listed in this chart, maybe 10 times more! In the recent past, many electronic companies had their own unix releases. This diagram is only the tip of an iceberg, with a penguin on it ;-).

If you want to print this timeline, you can freely download one of the following PDF files: