GMail Labs is a kind of plugin for GMail which is being trialed.
Labs for Google product means a kind of plugins that are currently in the experimental stage that eventually may become a standard feature. I liked some of new features are under development, GMail Labs, which I put to my account. Will be discussed one by one below.
This feature allows you to insert pictures to body email, not as an attachment. So email sent looked like one complete document. Contains text and images as a complement.
After Inserting Images feature is installed, you just click to add pictures. The images can be added from the computer (upload) or from the Internet (URL).
Default Text Styling
Feature that lets you use different font formats from GMail standard, and it could be the new standard default font format.
Mark as Read button
This button accelerates your step to mark the message (many) as already read a lot.
Disable GMail Labs
Disable Gmail Labs is necessary if the problem persists, you might have trouble to check email in your inbox. Trying to go to your email inbox through this link: https://mail.google.com/mail/u/0/?labs=0.
Related: GMaps Labs – distance measurement tool.