How do enable UNDO option in your gamil accounts

This is the google gmail feature to enable the UNDO option in your gmail account, is generally used for the undo segments whether any email missed by your mistake...so here I am providing some of the instruction to enable Undo optoin..like

1.Now first Go To your google labs and then Gmail labs on the top- right side of screen

[or sign in your mail id and goto setting-> click Labs tab]

2. now scroll down and find out Undo Send and Enable the option. now save your setting and view like that when u have an undo segment just like an top image..