Diagrams don’t just explain systems—they expose gaps, map flows, and clarify complexity. This book is your essential guide to leveraging Mermaid. js, a lightweight, text-based diagramming tool that lives right inside your Markdown, VSCode, or browser. Whether you're a seasoned network architect or a cybersecurity educator, you’ll learn how to create powerful visuals for secure systems—without leaving your dev environment. What you’ll sequence diagrams, class models, and Gantt charts—built with simplicity Real-world scenarios from home networks to cloud infrastructure Step-by-step exercises and visual blueprints for network and security contexts Platform-specific setup guides (Windows, Linux, macOS) Side-by-side comparisons with PlantUML for multi-tool fluency With a strong focus on interactive documentation, role-based architecture, and clear communication, this book empowers you to document as you think and build as you explain.