Expo is a simple and straightforward way to get a visual
impression of all your current virtual desktops that many
compositing window managers use. It's not a very powerful
approach, but a very intuitive one and especially fits workflows
that use lots of temporary windows or those in which the
workspaces are mentally arranged in a grid.

i3expo emulates that function within the limitations of a
non-compositing window manager. By listening to the IPC,
it takes a screenshot whenever a window event occurs.
Thanks to an extremely fast C library, this produces negligible
overhead in normal operation and allows the script to remember
what state you left a workspace in.

The script is run as a background process and reacts to signals
in order to open its UI in which you get an overview of the known
state of your workspaces and can select another with the mouse or
keyboard.