In the previous chapter, we learned that the executables generated by the .NET compilers are called assemblies. Under .NET, assemblies form the fundamental building block of program components. In defining the format for the assembly, .NET had many goals. These goals included interoperability among different programming languages, side-by-side execution of multiple versions of the same assembly, performance enhancements, and so on. In this chapter, we take an in-depth look at the assemblies and examine how these goals were achieved. By the end of the chapter, you will have a good knowledge of the assembly internals and the packaging and deployment model under .NET.