Sanjeevani is a magical herb (Selaginella bryopteris) mentioned in the Ramayana when, Lakshmana is badly wounded and is nearly killed by Ravana. Hanuman was called upon to fetch this herb from the mount Dronagiri a.k.a. Mahodaya in the Himalayas. Sushena took the life-giving plant and made Lakshman to smell its savour, so that he rose up whole and well.
In Hindu mythology, Sanjeevani is a magical herb which has the power to cure any malady. It was believed that medicines prepared from this herb could revive a dead person. Herb is mentioned in the Ramayana when, Ravana's son Indrajit hurls a powerful weapon at Lakshmana. Lakshmana is badly wounded and is nearly killed by Indrajeet. Hanuman was called upon to fetch this herb from the mount Dunagiri (Mahodaya) in the Himalayas or Valley of Flowers. Upon reaching Mount Sumeru, Hanuman was unable to identify the herb and decided to lift the entire mountain and bring it to the battlefield.
While some references in scientific literature list Selaginella bryopteris as the Sanjeevani mentioned in Hindu mythology, a search of ancient texts currently underway in CSIR laboratories has so far not revealed any plant that can be definitively confirmed as Sanjeevani. In certain texts it is written that Sanjeevani glows in the dark.