1) The Amazon Rainforest, located in South America, is the largest tropical rainforest in the world, covering an area of approximately 5.5 million square kilometers (2.1 million square miles). It is known for its exceptional biodiversity and plays a crucial role in the global ecosystem.

2) The world's oldest tree is believed to be a bristlecone pine named "Methuselah" in California, estimated to be over 4,800 years old.

3) The concept of self-driving cars, or autonomous vehicles, is being actively developed by companies such as Tesla, Google (Waymo), and Uber.

4) The President of the United States serves as the head of state and the head of government, responsible for leading the executive branch and representing the nation domestically and internationally.