1) The deepest part of the ocean is the Mariana Trench, reaching a depth of about 36,070 feet (10,994 meters).

2) The first modern health insurance policy was introduced in Germany in the late 19th century.

3) The development of blockchain technology, first introduced in 2008 with the creation of Bitcoin, has enabled secure and decentralized digital transactions and led to the emergence of cryptocurrencies.

4) Serena Williams is an American professional tennis player widely regarded as one of the greatest athletes in the sport. She has won numerous Grand Slam titles and Olympic gold medals and has become an influential figure both on and off the tennis court.