In Spring, understanding the difference between a Prototype and a Singleton bean is crucial to writing clean, scalable code. These two scopes, while different in behavior, often need to interact with each other in a Spring application. The challenge comes when you need to inject a Prototype bean into a Singleton, and ensure that every time the Prototype bean is requested, a new instance is created. If not handled carefully, this injection can lead to unexpected behavior that may not fit the design intentions of your system. This article dives deep into how to inject a Prototype bean into a Singleton in Spring, explains the underlying principles, and showcases a step-by-step code example that demonstrates this interaction. By the end of this guide, you will not only understand how to manage this injection properly, but also learn how to apply these techniques in your applications. Let's explore how Spring handles these bean scopes and discover a few secrets to mastering their injection.