Do I need to declare class as public or declare class_initialize as public?

Hello,
I have a ActiveX exe project and a standard project. My standard project reference ActiveX exe project.
To make it simple, I have one class module in the ActiveX exe project and I need to create an instance of the class in a new thread in the Standard project. These are how I've been tring:
In the standard exe:
Dim objMyClass As ProjectName.MyClass
Set objMyClass = CreateObject(ProjectName.MyClass);

I get the object successfully ONLY IF I have class_initialize in MyClass as Public or I have THIS LINE at the beginning of my MyClass module
Class MyClass As MyClass

I'm not sure how vb6 make a class publicly creatable and I don't know why what I tried works. I just guess and that works for me. I'd like to know WHY if anyone can help me really appreciate it. I've checked MSDN but no luck until now. Thanks all.