This post introduces the S.O.L.I.D. principles by Robert C. Martin and their application in React function components. Through a Task Manager application case study, it demonstrates the importance of the Single Responsibility Principle (SRP) and the Open/Closed Principle (OCP) in building scalable and maintainable React applications. The article contrasts poor and good component hierarchies, emphasizing the value of modular design, reusable components, and consistent naming conventions. It also highlights best practices and common pitfalls when applying these principles.