Markets on Wall Street and in Europe declined rapidly early Friday morning after President Donald Trump posted a pair of tariff threats on social media, one aimed at Apple and the other at the European Union.

President Donald Trump brought back up the idea of American-made iPhones on Friday when he threatened a 25% tariff on Apple.

As this special report shows, financial innovation has transformed Wall Street. As in eras past, surging asset values have concealed cracks in the new financial order. Whatever dangers are lurking, Mr Trump’s presidency will make them more dangerous still. ■

Newly sworn-in Social Security chief Frank Bisignano, who previously was a Wall Street executive, told staffers he had to Google the SSA job when it was offered to him.

Bond yields inched higher and Wall Street flipped from small gains to losses before the opening bell Thursday after rising U.S. debt sank markets on the previous day. Futures for the Dow Jones Industrial Average fell 0.5% in premarket trading, while futures for the S&P 500 and Nasdaq each slid 0.3%.

When stocks plunged in early April after the announcement of President Donald Trump’s tariffs, Noah Hackett knew what to do. The 19-year-old student at West Chester University, a public college in Pennsylvania, bought the dip.

Residents balked at a small traffic circle at Greenlawn Avenue and Wall Street near Potawatomi Park, saying it may worsen traffic.

Third Point's Dan Loeb is swapping out one of Wall Street's most influential businesses for another innovative leader.