Mobigel Research Library comes a very small tip on ‪#‎vi‬ editor or‪#‎vim‬ editor on ‪#‎Linux‬ . 

You all are using vim since your early days of exploration with Linux, and no doubt its a wonderful text editor. And I seriously thought couple of times, whether to post this post or not to post this post.

Now consider this:

You had opened a very important file in Linux using vim editor and had done couple of changes and now you want to revert back to original state of the file. PS: considering that you hadn't saved your changes using ESC+w command. 

You can achieve this by pressing ESC+u multiple times and it will work. But you know, you can also use ESC+e! or ESC+edit! to undo all the changes since you had opened the file, before saving, in just one command.