Reach an object from another class then the creation class

Question

Do anyone know how to reach the object "objX" from class Z, if "objX" is created from class Y and is an instance of class X ? I believe it's possible to do so when using Unsafe Code, since it's all about a reference to a memory address, but I would like to avoid Unsafe Code. The main problem with not using Unsafe Code, as far as I can see it, is the GC. But hopefully there's a way to work around it. Regards,