"Cobalt" is an open source virtual world browser and construction toolkit application being developed at Duke University. Cobalt will make it possible for people to easily create, publish, access, and participate in a network of linked virtual worlds. Currently in pre-alpha and built using the Croquet open source software platform, Cobalt uses peer-based messaging to eliminate the need for virtual world servers and makes it very simple to create and share secure virtual worlds that run on all major software operating systems.