Children playing on Walled City rooftop in Hong Kong, 1989. The lack of formal governance in the Walled City led to challenges, but it also fostered a unique system of informal social order. (Photo by Greg Girard/The Guardian)

“The Challenge!” Young boy relishes in a game of tug of war before school. Photo location: Lake Titicaca, Peru. (Photo and caption by Paul Heyman/National Geographic Photo Contest)

German kickboxer Christine Theiss (L) hits challenger Olja Zerajic of Bosnia during their WKA middleweight title fight at Postpalast on March 2, 2012 in Munich, Germany. (Photo by Alexandra Beier/Bongarts/Getty Images)

Hikaru Cho believes that we should challenge our imaginations to create new work using traditional tools, not fancy computers and software. (Photo by Jim Marks/PA Wire)

A Maori warrior prepares to challenge Prince Charles during his welcome to Takanhanga Marae in Kaikoura, New Zealand November 23, 2019. (Photo by Tracey Nearmy/Reuters)

A physically challenged girl looks at her brother as she is kept in a basin to seek alms from people on the street in Kano, Nigeria December 30, 2015. The girl has suffered from her condition since birth. (Photo by Reuters/Stringer)

Participants race during the Red Bull Box Cart Race challenges in Bo Kaap, one of the iconic neighbourhoods in Cape Town, South Africa on November 6, 2022. (Photo by Esa Alexander/Reuters)

Models present creations by DAQQAB during the Petjoy Fashion Week in Shanghai, China, 02 November 2025. The 2025 Petjoy Fashion Week runs from 31 October to 02 November at the Shanghai Fashion Center. (Photo by Alex Plavevski/EPA)