insert escape charactor within VIM

Hi,
I need to send "^[" command to the buffer.
I tried to use insert within VIM and press 'ctrl' key and then '^' and '[' key.
but it didn't work.

Does anyone know how to do it?

Thanks a lot!
Julie

'ctrl' + 'v' + '['
(with 'ctrl' being pressed)

Thank you and you are great!!!