Nested Labels are enabled at Gmail

Gmail blog has published and announcement. The said that nested label feature is now enebled in Gmail. Here is a snapshot at the left side. How to get it in Gmail inbox? If you like to use it, go to the Gmail Labs tab under Settings, and look for "Nested Labels". Now enable it and click "Save."

Now it is time to create some label. Name label with slashes (/) to make it the child of another. As example, let's say you wanted to create a simple hierarchy with a "Home" label, and inside it a "Members" and a "Jobs" label. Just create three labels with the following names:

Home
Home/Members
Home/Jobs

If you want, you can then create "Home/Members/Kids," "Home/Pets," etc.
In Gmail blog official said that :

You can create complex hierarchies of labels if that's the way you like to organize your mail, and you can expand/collapse labels to save space. You'll always be able to tell whether a given label contains unread messages in its collapsed child labels by looking at whether it's bold or not.

Read more tweaking at Gmail blog.