No application encryption key has been specified. New Laravel app

New to laravel and trying to use:

 "php artisan serve"

Displays

Laravel development server started: <http://127.0.0.1:8000>

But won't automatically launche, when I manually enter http://127.0.0.1:8000 it shows this error:

RuntimeException
No application encryption key has been specified.

Any ideas? Using Laravel Framework 5.5-dev

via Chebli Mohamed