The MIT Media Lab’s Reality Virtually Hackathon concludes tomorrow, January 21, with a Public Expo, 2PM-5PM, to showcase cutting-edge developments in augmented reality and virtual reality created by the hackathon’s 400 participating developers, designers, and AR/VR storytellers. It takes place at the Media Lab (75 Amherst Street, Cambridge). Registration is required and free, and a donation is requested (suggested $10 per person) to support the group’s future work.