Hera

Hera, the beautiful queen of Olympus, was a very jealous wife. Even Zeus, who was afraid of nothing, feared her  fits of temper. She hated all his other wives, and when Zeus first asked her to be his wife, she refused. Slyly Zeus created a thunderstorm, changed himself into a little cuckoo, and, pretending to be in distress, he flew into Hera's arms for protection. She pitied the wet little bird and hugged it close to keep it warm, but all of a sudden she found herself holding mighty Zeus in her arms instead of the bird.
Thus Zeus won Hera and all nature burst into bloom for their wedding. Mother Earth gave the bride a little apple tree that bore golden apples of immortality. Hera treasured the tree and planted it in the garden of the Hesperides, her secret garden far to the west. She put a hundred-headed dragon under the tree to guard the apples and ordered the three Nymphs of the Hesperides to water and care for the tree.

Zeus loved Hera dearly, but he was also very fond of rocky Greece. He often sneaked down to earth in disguise to marry mortal girls. The more wives he had, the more children he would have, and all the better for Greece! All his children would inherit some of his greatness and become great heroes and rulers. But Hera in her jealous rage tormented his other wives and children, and even Zeus was powerless to stop her. She knew how tricky Zeus could be and kept very close watch over him.
One day as Hera looked down on earth, she spied a small dark thundercloud where no cloud should have been. She rushed down and darted into the cloud. Zeus was there just as she had suspected, but with him was only a little snow-white cow. He had seen Hera coming and, to protect his newest bride Io from her wrath, he had changed the girl into a cow. Alas! The cow was as lovely as the girl, and Hera was not deceived, but she pretended to suspect nothing and begged Zeus to let her have the dainty cow. Zeus could not well refuse his queen such a little wish without giving himself away, and he had to give her the cow. Hera tied poor Io to a tree and sent her servant Argus to keep watch over her.
Argus had a hundred bright eyes placed all over his body. He was so big and strong that singlehandedly he had made an end to the monstrous Echidna, who had lived in a cave and had devoured all who passed by. He was Hera's faithful servant and the best of watchmen, for he never closed more than half of his eyes in sleep at a time.
Argus sat down next to the cow and watched her with all his eyes, and poor Io had to walk on four legs and eat grass. She raised her mournful eyes to Olympus, but Zeus was so afraid of Hera that he did not dare to help her. At last he could no longer bear to see her distress, and he asked his son Hermes, the craftiest of the gods, to run down to earth and set Io free.
Hermes disguised himself as a shepherd and walked up to Argus playing a tune on his shepherd's pipe. Argus was bored, having nothing to do with all his eyes but watch a little cow, and he was glad to have music and company. Hermes sat down beside him, and after he had played for a while, he began to tell a long and dull story. It had no beginning and it had no end and fifty of Argus's eyes closed in sleep. Hermes droned on and on and slowly the fifty other eyes fell shut, one by one. Quickly Hermes touched all the eyes with his magic wand and  closed them forever in eternal sleep. Argus had been bored to death.

Hermes then untied the cow, and Io ran home to her father, the river-god Inachos. He did not recognize the cow as his daughter, and Io could not tell him what had happened, all she could say was, "Mooo!" But when she lifted up her little hoof and scratched her name, "I- O," in the river sand, her father at once understood what had happened, for he knew the ways of Zeus. Inachos rose out of his river bed and rushed off to take revenge on the mighty thunder-god. He flew at Zeus in such a rage that to save himself Zeus had to throw a thunderbolt, and ever since the bed of the river Inachos in Arcadia has been dry.
Hera was furious when she saw that Argus was dead and the cow Io had been set free.
She sent a vicious gadfly to sting and chase the cow. To be sure that her faithful servant Argus would never be forgotten, she took his hundred bright eyes and put them on the tail of the peacock, her favorite bird. The eyes could no longer see, but they looked gorgeous, and that went to the peacock's little head, and made it the vainest of all animals.
Pursued by the gadfly, Io ran all over Greece. Trying to escape from its tormenting sting, she jumped across the strait that separates Europe from Asia Minor, and, ever since, it has been called the Bosporus, the "cow ford."
But still the gadfly chased her all the way to the land of Egypt. When the Egyptians saw the snow-white cow, they fell to their knees and worshiped her. She became an Egyptian goddess, and Hera now permitted Zeus to change her back to her human shape. But first he had to promise never to look at Io again.
Io lived long as the goddess-queen of Egypt, and the son she bore to Zeus became king after her. Her descendants returned to Greece as great kings and beautiful queens. Poor Io's sufferings had not all been in vain.