In my previous article, What is OWIN? A Beginners Guide we learned the basics of OWIN and the benefits it brings to building web application in Asp.Net frameworks. We have also learnt to build a very simple application using Project Katana and different ways to deploy OWIN application in the next article Creating Our First OWIN Based Application. These articles helped us to understand what IAppBuilder interface is and how the Owin host tries to find the Startup class and bootstrap the application. In this article, let’s understand the OWIN middleware components, their usages, and different ways of building middleware components.