Complex systems theory studies how various components interact within a system, leading to behaviors that are not predictable from the individual parts alone. These systems can be found in nature, society, and technology, where elements like ecosystems, economies, and social networks exhibit intricate relationships and feedback loops. The theory emphasizes that small changes can have significant impacts, a concept known as sensitivity to initial conditions. This unpredictability makes it challenging to model and understand complex systems, but it also reveals the richness and diversity of behaviors that emerge from simple rules and interactions among the components.