Asclepius was the Greek god of healing and medicine.

Before Asclepius magical healing had been largely confine to hero shrines that were only of local importance. He was the first person to become a major god. Worship of Aesclepius began as a group of followers that were related to him, but this soon developed into a huge cult.

It is generally thought that his career as a physician began with a devoted but local clientele. In Homer's Iliad he is depicted as an ordinary man, not a god, the ruler of a region of Thessaly and nearby towns where he shared the secrets of the healing arts. There is little about him in myth other than his birth and death. Pindars Othyian Ode 3 identifies Asclepius as the son of Apollo, a god closely associated with healing and a mortal woman called Koronis. According to mythology Koronis betrayed Apollo who slew her but snatched her unborn child from the flames of her funeral pyre:

But when her relatives had placed the girl With the pyre's wooden wall and the fierce blaze Of Hiphaistos ran around it, then Apollo said: 'No longer Shall I endure in my psyche to destroy my own off spring By a most pitiful death (thanatos) Along with his mother's heavy suffering (pathos). Thus he spoke and with his first stride Came and snatched the child From the corpse While the burning flame parted for him. He took him and gave him to the Magnesian Centaur For instruction in healing the diseases that plague men

( pp. 38-46 Translated by William Race. Quoted in Lecture by Thomas E. Jenkins)

Asclepius was the first to institute the practice of medicine and the art of Pharmacology. Other sources reveal that he acquired these skills using herbs that had been spilt on the Thessalian plain by a sorceress Medea. Chirion, who adopted Asclepius, taught him all his medical skills. At this time he tended the serpents on Mount Pelion who taught him the secret knowledge of herbs.
He attracted the favour of Athena who gave him some of the gorgon's blood which possessed the divine power to revive the dead. This angered Hades who complained to Zeus, who in turn suspended Asclepius from medical practice, then killed Ascelpius with a thunderbolt. The mythographer Apollodorus writes:

'Having become a surgeon and having developed his skills to a high degree, he not only prevented people from dying, but even brought them back to life for he had received from Athena the blood that flowed from the veins of the Gorgon and while he could use the blood that flowed from her left side to take away human life, he used the blood from her right side to bring them back to life. This is how he managed to raise people from the dead. But Zeus, fearing that people might learn this healing art from him, and so rescue one another from death, struck Asclepius with a thunderbolt. In order to get his own back, Apollo slew the Cyclopes who had manufactured the thunderbolt for Zeus.'

Diodorus, writing in the late first century BC expanded further the reasons for Zeus' anger:

'Asclepius' reputation became so great that he cured many who had not expected to recover and this is why he seemed to have brought so many back to life. This is the origin of the story that even Hades brought a charge against Asclepius, accusing him before Zeus on the grounds that he was losing his powers; for the dead were constantly becoming fewer, because they were being healed by Asclepius'

It is difficult to define or date where and when the worship of Asclepius started but it flourished in Epidauros. Other healers were worshipped there before him, including Apollo, but by the 5th Century Apollo was ousted by Asclepius and similarly in Corinth.