First, thanks to Karl's answer. I have only minor correction to this.
My scenario:
Millions of folders inside /source/directory, containing subfolders and files inside. Goal is to copy it keeping the same directory structure.
To do that I use such command:
find /source/directory -mindepth 1 -maxdepth 1 -name '*' -exec mv {} /target/directory \;
Here:
- -mindepth 1 : makes sure you don't move root folder
- -maxdepth 1 : makes sure you search only for first level children. So all it's content is going to be moved too, but you don't need to search for it.
Commands suggested in answers above made result directory structure flat - and it was not what I looked for, so decided to share my approach.