The SOLID principles emerged from 1970s software engineering crises when monolithic systems became unmanageable. Robert C. Martin introduced these five design guidelines to replace spaghetti code with modular, maintainable architecture. They transform software development from an artisanal craft into a disciplined engineering practice.

Single Responsibility Principle is the first pillar: a class should have one reason to change. In practice, this means separating concerns like business logic, database operations, and email communication into distinct classes. The article contrasts monolithic 'God Objects' with modular components that fit together like LEGO bricks.

Modern frameworks like Clean Architecture and CQRS implement SOLID through patterns like Command Handlers. A `CriarPedidoHandler` might manage order creation while delegating persistence to a repository and notifications to event handlers. This separation allows independent evolution of database layers or communication channels without breaking core business rules.