In this chapter, we are going to bring together all the concepts we've discussed with a sample business network, involving a real-world example. Specifically, we're going to do a detailed walk-through of the Hyperledger Composer letter of credit sample, so that you can understand how participants, assets, transactions, and events are realized in code. We'll show how the business network is used, analyzed, defined, and how that definition is used to generate APIs, test them, and integrate them into a sample application. This is going to be a comprehensive tour that will get you from concepts right into implementation. We're going to use the letter of credit sample because it represents a well-known process that's often discussed in relation to blockchain. Let's discuss the process first, and then see why it's used as the poster child example.