1) The Eiffel Tower can be 15 cm taller during the summer due to thermal expansion.

2) The Internet of Things (IoT) refers to the network of physical devices, vehicles, appliances, and other objects embedded with sensors, software, and connectivity.

3) The ancient city of Athens, Greece, is often considered the birthplace of democracy, where citizens had a say in the decision-making process.

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.