Microsoft announced Windows Hello a few months ago, but has been rather quiet on the feature since. Windows Hello is a new form of security for your Windows PC which allows you to login with your face. It requires special hardware with IR sensors which checks to make sure it is actually you trying to login.
Windows 10 build 10125 finally has the option to use Windows Hello, and setting it up is very easy. The option is in the sign-in options in the Settings app, and also requires a PIN to be set before Windows Hello can be enabled.
As said above, this features requires hardware in which we do not have access to, so we're unable to actually show it to you in action. However we can show you the setup process.
There's a small amount of customization for Windows Hello too. You can turn automatic unlock once it detects your face on and off, and you can add extra security measures by requiring Windows to look at not only the front, but both sides of you face as well.
Stay tuned at WinBeta for more news regarding Windows 10 leading up to RTM in a couple months. Windows 10 build 10125 is an unreleased and unleaked build.