Users of Google’s Gmail service can now send SMS text message chats to mobile phones using the built-in Chat feature using a new experimental feature in GMail Labs, reports Webmonkey.

To turn it on, you need to go to the Labs tab within Gmail’s settings or click on the little green conical flask icon next to your e-mail address at the top of the page. If you don’t see the option right away, check back later as it will be made available in Labs to all users Thursday evening.

Once the option is turned on, start typing a phone number into the Chat’s search box and you’ll see the option to send an SMS.

If you already have your friend’s phone number stored in your Google account’s contacts, try searching for them by name. When your friend’s name appears in the drop-down list of contacts, you’ll see an option to send them an SMS. You can also hover over or click on anyone in your Chat buddy list to send them an SMS.

The first time you send a text message, it will appear on the recipient’s cellphone as coming from a 406 area code number. Google has made several thousands of these numbers available for Gmail users, and once a number is associated with your account, all text messages that you send through Gmail will come from that number.

The 406 number works both ways, so your friend can reply to you via text message. Also, your friend can associate that number on their mobile phone with your contact details so that they can initiate new chat sessions with you, anytime.