While Gmail features don't exactly roll out in the most traditional way, they do tend to add pretty useful functionality to Google's ever-so-popular webmail service. Now, as showcased on The Official Gmail Blog, available in Gmail Labs are two new features for your testing pleasure: Nested Labels, and Message Sneak Peek.
Nested Labels is exactly what it sounds like. Just like you can do in Outlook, Gmail now allows you to put sub-labels within parent labels. However, the UI for doing so is still non-existent (hopefully this will change in the future). To create a nested label, you have to use a specific naming convention when you create a label. For example, if you wanted a parent label called "Favorite People" with sub-labels called "Neowinians" and "Androids," you'd have to name them as follows:
The above will result in a folder structure similar to the one in the picture above. If a label has nested labels within it, there will be a "+" sign to expand the label tree, and a "-" to close it.
Message Sneak Peek is Gmail's way of giving a preview of your emails without actually having to go into them. Taking a peek does not mark an email as read. When you right click on an email that's in your inbox, a nice sized box pops up showing you the email's contents. Within the preview, you have the ability to archive, delete, or mark the email as read. You also have the option to view the email in its entirety.