<a href="https://en.wikipedia.org/wiki/World_War_II" id="mwmQ" rel="mw:WikiLink" title="World War II">World War II</a>: During the <a href="https://en.wikipedia.org/wiki/Manhattan_Project" id="mwmg" rel="mw:WikiLink" title="Manhattan Project">Manhattan Project</a>, a team led by <a href="https://en.wikipedia.org/wiki/Enrico_Fermi" id="mwmw" rel="mw:WikiLink" title="Enrico Fermi">Enrico Fermi</a> initiates the <a href="https://en.wikipedia.org/wiki/Chicago_Pile-1" id="mwnA" rel="mw:WikiLink" title="Chicago Pile-1">first artificial self-sustaining nuclear chain reaction</a>.