Demon King Bali had conquered the three worlds the devtas were no match for this powerful Asur king so they requested Lord Vishnu to help them out .Lord vishnu disguised himself as Vamana small brahmin boy and approached King Bali while he was performing a yagna ,he asked King Bali for three steps of land ,the demon king readily agreed for this but the demon guru shukracharya saw through the design of Lord Vishnu,therefore he tried to dissuade King Bali but could not make him to agree so he blocked the spout of water vessel of King Bali, Vaman the vishnu avataar took out a sharp blade of grass to clear the obstruction. As he poked towards the pot's spout, the blade of the grass destroyed one of Shukracharya's eyes, and this is the reason why Shukracharya is seen to have one eye ever since.
With the obstacle successfully removed and the ritual over, it was time for the Vaman to take his 3 strides worth of land. But suddenly, the vaman boy's size started to increase in size until no one could see his head anymore. In one stride, he took both the netherworld/hell and the earth, and in the 2nd stride, he took heaven. Then Vaman avataar of Vishnu Ji turned around towards Bali and asked "Now where do I put my 3rd foot?" Bali offered his own head for the vaman jis third stride.