PART III Structural Patterns Container images and containers are similar to classes and objects in the object- oriented world. Container images are the blueprint from which containers are instan‐ tiated. But these containers do not run in isolation; they run in other abstractions such as Pods, which provide unique runtime capabilities. The patterns in this category are focused on structuring and organizing containers in a Pod to satisfy different use cases. The forces that affect containers in Pods result in the patterns discussed in the following chapters: • Chapter 14,  Init Container , introduces a separate lifecycle for initialization-related tasks and the main application containers. • Chapter 15,  Sidecar , describes how to extend and enhance the functionality of a pre-existing container without changing it. • Chapter 16,  Adapter , takes an heterogeneous system and makes it conform to a consistent unified interface that can be consumed by the outside world. • Chapter 17,  Ambassador , describes a proxy that decouples access to external services.