When editing a file in nano I tend to hit ctrl-z to attempt to undo an edit but when you press ctrl-z in nano it dumps you back in the shell... very confusing... and very annoying because I do this all the time and usually just started over using a new nano instance.

It turns out ctrl-z is a global command to send the current process to the background (not just nano) and here's a way to get a background process back, simply type:

fg 

and nano will be back in the terminal as it was before hitting ctrl-z. Hooray!

If there are multiple processes in the background
you can run jobs which will give you a list of processes running in the background:

[1]+  Stopped        nano fileimediting

To bring job nr 1 to back to the foreground run fg 1, simple as that.