Vamana was his fifth incarnationVamana means a DwarfThere is an interesting story behind this avatharam.Emperor Mahaballi (he is the grand sun of Prahaladan) ruled over the Pathala-loka. Instead of being confined to his-loka he captured the other lokas and was ruling over them.

The Gods and others from other lokas Implored to God to put Mahabali in his place.Once Mahabali was performaing a big "yaga"( offering things in the sacrificial fire) and at the end of the yaga was giving away gold and other things in charity.

Whoever went to the palace on that day could ask whatever they wished and the king would certainlyoblige them.God seized this opportunity and came to Mahabali's palace as adwarf-mendicant. The dwarf asked the King for just 3 foot-measure of land for himself. The king was perplexed and wondering why the dwarf was asking for only a 3 foot-measure of land when he could ask for acres and acres of land. However the king agred and asked the dwarf the measure the land with his feet. ho! God assumed gigantic proportions his head reaching up to the sky - the highest world above and his feet down at Pathala-loka the lowest of the worlds below the earth .God took one step and that covered all the worlds above the second step covered all the worlds below and there was no place left for his third foot measure. God asked king " Mahabali , I have taken two steps and have covered all the lokas tell me where to keep my foot for the third foot-measure."

Mahabali realising that the dwarf was no other than God him self Bowed before the dwarf and said " Please my lord you may keep your foot over my head as the third measure." Accordingly God put his foot on Mahabali's head and pressed hard to push the King to 'Pathala'loka' and told him "O king! this is where you belong and you should confine your self to this loka only." Mahabali realised his folly and ruled long over Pathala-loka.This is to show the people that they should live in their own place sand should not be so greedy to occupy the other lands.This was the Lord's fourth incarnation - as a dwarf.