(Image above is taken from Lifehacker)

Feeling bored with the current features offered by Gmail? Wanted to try something new from the Gmail Lab?

You got it. Recently, I read an article from Lifehacker that teach me how to enable it. Just copy and paste the link in your URL: https://mail.google.com/mail/?labs=1#settings

As the "Lab" word suggests that the features are still in experimental stage, hence, Google will not be responsible for any mishaps. I tried it, so far so good.

Have fun.