Regional integration has been a major focus for scholars studying how different regions work together. There have been four waves of regionalism since the 19th century, with the most recent wave happening in a more globalized world. This new regionalism has led to changes in how regions cooperate, affecting trade, politics, security, culture, and institutions. The way we analyze regional integration has also improved over time, with new theories helping us understand how regions work together. There are still some things we need to study further, but overall, regional integration is a complex process with many implications for how countries interact with each other.