In its simplest form the papal tiara seems to have appeared about the third century. Over the years it became much more ornate and took on a kind of beehive shape.
The tiara came to consist of three crowns. According to James Charles Noonan, Jr., in The Church Visible, the bottom crown became ornamentation at the base of the miter in the ninth century. When the popes assumed temporal power, the base crown became decorated with jewels to resemble the crowns of princes. A second crown was added by Boniface VIII in 1298 to symbolize spiritual dominion. Very soon after, a third crown and lappets (cloth strips) were added.
According to Noonan, the triple tiara represents the pope’s universal episcopate, his supreme jurisdiction and his temporal power. It is also said to represent his role as priest, pastor and teacher.
In our century the tiara came to be regarded as inappropriate because of its ornateness and rich character. Pope Paul VI stopped wearing the tiara and sold his, using the funds for the poor.