This Monday, September 15, 2014 photo shows glazed bricks displayed at the Iraqi National Museum in Baghdad. The Islamic State militants seek to purge society of all influences that don't conform with their strict, puritanical version of Islam. That means destroying not only relics seen as pagan but also Muslim sites they see as contradicting their ideology, particularly Sunni Muslim shrines they see as idolatrous as well as mosques used by Shiites, a branch of Islam they consider heretical. (Photo by Hadi Mizban/AP Photo)

In this Monday, March 10, 2014 photo, a 9,000 year-old mask is on display at the Israel Museum in Jerusalem. The exhibition called “Face To Face” shows eleven stone masks, said to have been discovered in the Judean desert and hills near Jerusalem, which date back 9,000 years and offer a rare glimpse at some of civilization's first communal rituals. (Photo by Tsafrir Abayov/AP Photo)

Members of Japanese idol group Kamen Joshi (Masked Girls) pose for a photo after a rehearsal for a concert at their theatre in Tokyo's Akihabara district, Japan March 17, 2016. For countless girl and pop-idol bands in Japan, standing out from the crowd can be daunting, but one group – “Kamen Joshi” – seems to have found the answer by hiding behind masks. The Tokyo-based all female band has 18 members, split into three groups that perform across Japan and elsewhere in Asia. (Photo by Toru Hanai/Reuters)

A man dressed as a devil poses next to a grafitti of late rebel hero Ernesto "Che" Guevara in the indigenous community of Monimbo in Masaya, Nicaragua, October 16, 2015. People prepare to participate in the popular annual festival called "The Aguizotes" held on the last Friday of October, where residents dress up as characters from legends and folklore mythology of Nicaragua. (Photo by Oswaldo Rivas/Reuters)

A boy performs a masked dance as he participates in a parade during the National Encounter of Mask festival in Barva de Heredia October 30, 2015. (Photo by Juan Carlos Ulate/Reuters)

Three workers demonstrating the different types of gas masks used in mine rescue work. (Photo by Fox Photos/Getty Images). December 1925

A member of the “Los Danzantes y Los Boteiros” folk group performs during the parade of the 10th International Festival of the Iberian Mask in Lisbon, Portugal May 9, 2015. The festival runs until next Sunday and about 690 masked people from Spain and Portugal are participating, according to organizers. (Photo by Rafael Marchante/Reuters)

A fireman from the London Fire Brigade, wearing a smoke helmet. (Photo by Topical Press Agency/Getty Images). Circa 1908