This text presents an ontological reflection on the relationship between structure and substance, arguing that while focusing on structure is essential to counter unexamined assumptions about substance, reducing everything to structure is flawed. The central inquiry examines the definition of structure as a network of relationships and connections. If structure is composed of relationships, a fundamental question arises: between what entities do these relationships exist? The author rejects attempts to solve this via infinite regression, such as defining structure as relationships between other relationships. It is argued that a relationship cannot exist in itself or as a connection between nothings; by definition, a relationship requires distinct elements to connect. Consequently, the nature of these underlying elements remains an open and unresolved problem. The text concludes that despite the importance of a structural approach, the actual character of the entities involved cannot be ignored or fully replaced by a system of pure relations without substance.