Seven-year-old Mimi Meade winces from the sting as Dr. Richard Mulvaney inoculates her April 26, 1954 in McClean, Va., with the new Salk polio vaccine. Mrs. John Lucas, a registered nurse, holds Mimi's arm steady as she gets one of the first injections of the countrywide test. (Photo by Harvey Georges/AP Photo)

Football fans watch a broadcast of the UEFA Euro 2020 round of 16 match between The Netherlands and Czech Republic on a terrace in Amsterdam, the Netherlands, 27 June 2021. Visitors had to be tested in advance and once did not have to keep a distance of 1.5 meters. As one of the relaxation of the corona measures, catering establishments are allowed to place large screens to show the matches. (Photo by Ramon van Flymen/EPA/EFE)

Bryan Berg was introduced to card-stacking by his grandfather at the age of 8. He is a self-taught artist in all of the techniques he uses today. Berg's freestanding card structures are based on a grid-like arrangement, which Berg tested in a structural engineering lab to support 660 lbs per square foot―using no tape, no glue, no folding, and no tricks.

A photographer tested the concentration of several pairs of dogs as he captured their reactions to treat time in a series of shots. Christian Vieler, 47, of Waltrop, Germany, has been a professional dog photographer since 2016. He came up with the idea of snapping two dogs catching treats simultaneously. Here: Basset Hounds. (Photo by Vieler Photography/Caters News Agency)

Former Soviet President Mikhail Gorbachev and his daughter Irina Virganskaya attend the Free Your Mind Award Presentation at the Cinema For Peace charity dinner at the China Club on November 8, 2009 in Berlin, Germany. (Photo by Sean Gallup/Getty Images). BERLIN – NOVEMBER 08 2009

Adolf Hitler, Alfred Rosenberg (left) and Dr. Friedrich Weber of the Freikorps Oberland (Oberland Free Corps), during the Munich Putsch. (Photo by Keystone/Getty Images). 1923

Tao Xiangli gets out of his homemade submarine after operating it in a lake on the outskirts of Beijing September 3, 2009. Amateur inventor Tao, 34, made a fully functional submarine, which has a periscope, depth control tanks, electric motors, manometer, and two propellers, from old oil barrels and tools which he bought at a second-hand market. He took 2 years to invent and test the submarine which costs 30,000 yuan ($4,385). (Photo by Christina Hu/Reuters)