1) The Cuban Missile Crisis in 1962 brought the United States and the Soviet Union to the brink of nuclear war during the Cold War.

2) The world's largest volcano, Mauna Loa in Hawaii, is also one of the most active. It stands over 13,000 feet (4,000 meters) above sea level.

3) Serena Williams, an American tennis player, has won a total of 23 Grand Slam singles titles, making her one of the most successful players in the history of the sport.

4) The sunflower is not a single flower but a cluster of small flowers arranged in a spiral pattern.