If you are one of the lucky ones, you'll be able to invite up to 5 friends to join you – but with 1 million people signed up for it, there will be a whole lot of disappointed emailers later on.
If you've not heard about Wave, it's what Google describes as "how email would look if it were invented today", and features real-time typing. This means if you and a friend are both online at the same time it will revert to a IM-like service, allowing you to see what's being typed letter by letter.
All the messages sent can be edited by all the members of the exchange, and you'll also be able to drag and drop photos from your desktop, straight into a convo.
There's loads more fun things you can do which you can check out in Google's video, and you can also sign up your interest there as well.
Of course, if you're not one of the lucky ones getting an invite at 4pm, then you'll just have to wait until early 2010 when the email service opens its doors to everyone.
Make us green with envy by letting us know below if you get an invite, and be sure to check out what we think about the new email service.