Write a short account of Nanak's contribution to the Bhakti Movement.

Guru Nanak's teachings of nirguna worship (one formless God) and universal brotherhood formed the basis of a new religion called Sikhism. He was born in Talwandi (now Nankana Sahib in Pakistan) in 1469 CE, and his philosophical thirst made him visit the holy places of the Hindus, Muslims and Buddhists. He finally settled on the banks of the river Ravi and preached his teachings in a practical way. He started the guru ka langar or 'kitchen of the lord', where everyone, irrespective of caste and creed, ate together from a common vessel, striking at the core of the caste system which promoted inequality. He showed a new path for the establishment of an egalitarian social order. He was as much a social reformer as a religious teacher, and he upheld the cause of women, the downtrodden and the poor.