We love the terrarium necklace! These vintage watchmakers' vials are carefully planted with a tiny living specimen of moss. The charcoal at the base of the plant keeps the little ecosystem healthy. Open the vial and place a drop of water inside every 2-3 weeks, air it out occasionally, and store in indirect sunlight. If your moss does someday die, take a sample of moss from a favorite woodsy spot and re-plant your new terrarium.