Complex systems are collections of interconnected parts that interact in various ways, leading to behaviors that are not easily predictable. These systems can be found in nature, such as in ecosystems, where plants, animals, and microorganisms work together, or in human-made systems like traffic networks, where individual vehicles influence overall flow. The study of complex systems often involves understanding how simple rules can lead to intricate patterns and behaviors. Researchers in fields like biology, economics, and computer science analyze these systems to uncover underlying principles, helping to solve problems and improve decision-making in various domains.