1) The process of impeachment involves charging a public official, such as a president or high-ranking government official, with misconduct and potentially removing them from office through a trial and vote by the legislature.

2) The invention of the transistor by Bell Laboratories in 1947 revolutionized electronics and paved the way for the development of smaller, more efficient electronic devices.

3) The first modern Olympic marathon race was held at the 1896 Olympics in Athens and has since become one of the most iconic and challenging events in athletics.

4) The Great Wall of China is a UNESCO World Heritage site and one of the most iconic man-made structures in the world. It stretches over 21,196 kilometers (13,171 miles) and was constructed to protect the Chinese empire from invasions during ancient times.