Thangkas (Tib. Thang kha or Thang ka) are Tibetan hanging scroll paintings on cloth. They can depict deities, mandalas and all kinds of iconographic information.
Legend has it that the first ever thangka was made during the lifetime of the Buddha: in the Kalandaka region were two kings, Bimbi Sara and Udrayana. They used to send each other gifts from time to time and etiquette demanded that they always sent something more precious in return. When king Bimbi sara had exhausted all the material goods he could offer back to king Udrayana, he decided to send him a painting of Lord Buddha. This gift was considered far more valuable than all the riches of the three realms.
The very last things that are painted in a Thangka are the eyes. It is said that a thangka has opened its eyes after they have been made. The Thangka is then considered to be holy, but it is not to be worshipped unless a Lama has performed the formal rituals on it.