There are many small countries in the world based on both area and population. Nauru and Tuvalu are two very small countries that are islands located in the ocean. They are less than 10 square miles in area. The Vatican City and Monaco are both less than 1 square mile in area. These are actually located on a continent and are not islands.
Countries can also be compared by their populations. Vatican City has only 1,000 people whereas Monaco has about 38,000 which is typically the size of a small city and not a country. Nauru and Tuvalu have about 10,000 people each in their populations. Lichtenstein ranks 6th in the world for being the smallest countries. It has about 62 square miles with 37,000 people.