Google today announced today that Google’s new hangouts service/experience  would be available in Gmail:

What does this mean for your Gmail? You now have the option to switch from the current version of chat to Hangouts. Simply click “Try it out” next to your chat list to switch to Hangouts and give your chat an instant facelift (literally!). You’ll now see the profile photos in the order of your most recent conversations. With Hangouts, you’ll also be able to quickly send messages, have video calls with up to ten people at once, and share photos. You can start a conversation with just one friend or even a whole group.