In this session, we will explore the intricate details of Java class files beyond the commonly discussed bytecode. A key focus will be on the invokedynamic instruction and the attributes that enable its advanced capabilities, such as facilitating lambda expressions and optimizing string concatenation. We will also delve into the nestmates feature, which streamlines the interaction between outer and inner classes, enhancing both performance and flexibility in class file structure. Whether you are a seasoned Java developer or new to understanding the depths of the JVM, this session will provide valuable insights into the hidden layers of Java class files.