1) 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.

2) The concept of proportional representation, used in some electoral systems, aims to ensure that political parties' representation in government aligns more closely with the proportion of votes they receive from the electorate.

3) The croissant, a flaky and buttery pastry, is an iconic French delicacy. It is made by layering dough with butter, rolling and folding it multiple times to create a laminated structure. The croissant can be enjoyed plain or filled with various ingredients, such as chocolate, almond paste, or ham and cheese. It has become popular worldwide and is a staple in breakfast menus and bakeries, symbolizing French culinary expertise and savoir-faire.

4) The smallest unit of time is known as a zeptosecond, which is equal to one trillionth of one billionth of a second.