This step not only provides the big picture in which blockchain is located but also highlights its location within the big picture. To help you recognize the big picture, this step introduces the concept of software architecture and explains its relationship to separating a system into layers and aspects. To let you recognize the location of blockchain within the big picture, this step highlights the relationship between blockchain and software architecture. Finally, this step points out the core purpose of blockchain in just one sentence. Appreciating its purpose is a cornerstone for understanding blockchain and the course of subsequent steps.