Knock, knock! Millions of workers are going door-to-door in India. Some are making their way through crowded city streets. Others are trekking over snowy mountains or across thick forests.
It’s all part of India’s census, which began in April. A census is an official count of everyone living in a country.
Counting every person in India is a big challenge. About 1.4 billion people live there. It is the world’s most populous nation.
Some cities in India are among the most crowded on Earth. For example, more than 20 million people are packed into the city of Mumbai. That’s more than the population of almost every U.S. state!