Let admin log in as users (su for wordpress)

Hi

Does anyone know if there exist a plugin that let the admin log in as a normal user. Just like the ‘su’ command in linux.

I want to log in as admin, go to the user list and select a user. This should terminate the admin session and start a new session where I am logged in as the user I selected.

I have tried to use the wp_set_current_user function, but it does not seem to work the way I thought.