This e-book is your comprehensive guide to understanding agentic architectures, especially for retrieval-intensive applications. It discusses the fundamentals of agentic architectures including its components, the different between single-agent and multi-agent architectures, and atomic patterns of agentic architectures. Then, it walks through various examples of agentic architectures for retrieval-intensive applications, discussing the underlying considerations for each. This e-book provides a solid foundation for your journey into agentic architectures.