This lecture focuses on the core of Web Components, it will answer the What, Why and How we use it. For years, libs & frameworks in JavaScript tried to build components for reuse, but the solutions suffered partially or all from: capsulation, inability to import templates, reuse, no standards. Web Components is the solution, It solves all these troubling issues above for agility, to make the apps more flexible, reusable and stable. It modifies the development approach to be more microservices oriented.