Methods for expanding class in another class/struct

[IGotD-]

We know that classes are all reference typed so that classes must 
be allocated on the heap. However, this memory could be taken 
from anywhere so basically this memory could be a static array 
inside the class. This is pretty much what the scoped template 
does when allocating a class on the stack. In practice allocating 
a class inside another class could be done in similar fashion.

Do we have a good example showing how to expand a class inside 
another class?
Shouldn't be have a standard template similar to scoped, that 
statically allocates space inside the class? This template should 
be available in the standard library.