Bigelow Aerospace has been experimenting with the concept of inflatable space modules for quite some time, and they're finally ready to put it to a real test: at least two years docked to the ISS. Now, finally, ISS astronauts and cosmonauts can have those zero-g wrestling tournaments they want so badly.
The BEAM (Bigelow Expandable Activity Module) will be transported to the space station in the unpressurized 'trunk' of a SpaceX Dragon cargo vehicle. This will also make the BEAM module the first space station module (I believe) to be placed in orbit by a private, non-governmental spacecraft.
The initial BEAM module is not that large, but compared to the size it is when uninflected, it's pretty phenomenal. It inflates to something around the size of an MPLM — a Multi-Purpose Logistics Module that were once hauled up to the station by the space shuttle. Those carried cargo and added a bit of extra room on the station, but filled half the shuttle cargo bay. The BEAM module collapses small enough to fit in the Dragon's (relatively) tiny trunk area.
I'm sure the astronauts and cosmonauts on the ISS will really appreciate the extra area to move around in, and hopefully this experiment will prove successful enough that we'll end up seeing some really huge inflatable spaceships and stations in the future.
I'm curious to know how the micrometeroid protection is handled. I guess we'll learn all that starting next year, when it's set to launch.