Fireflies are networked nightlights for a local environment, the jars can be placed in different bedrooms or other spots around a home so people can communicate with one another through simply tapping on the jars. For example, if you tap the jar in your bedroom you will pulse the colored fireflies associated with that jar. The neighboring jars in your home will receive and pulse your taps, record them and then play them back. The neighboring jars can respond with their own tapping and broadcast themselves to the nightlights in the home. Pretty- here’s how to make them. Link.