The Ubuntu Filesystem Tree Lens is an Unity Lens that enables users to easily and quickly find files and folder in their filesystem, directly from Unity Dash.
When you click a folder, Nautilus will open it showing you the contents. When you click a file, it will be opened in an app that can view the respective file.
To install the Unity Filesystem Tree Lens plugin in your Ubuntu operating system, open a terminal window (hit the CTRL+ALT+T key combination) and paste the following commands (one by one, hitting Enter after each one):
sudo add-apt-repository ppa:jesse-imaginaryrobots/ppa
sudo apt-get update && sudo apt-get -y install fstree
You will need to restart your session after the installation. This Lens is available only for the Ubuntu 12.10 (Quantal Quetzal) operating systems.