Visual C++ debugger visualizer?

How does Visual Studio show the elements of a vector, or the characters of a string, in C++? Is there a way for me to make it show my own classes in a custom way?

http://msdn.microsoft.com/en-us/library/zf0e8s14(v=VS.100).aspx

For native code, you can add custom data type expansions to the file autoexp.dat, which is located in the Program Files\Microsoft Visual Studio 10.0\Common7\Packages\Debugger directory. Instructions on how to write autoexp rules are located in the file itself.

For this class:

template<class T>
struct  auto_array {
     T* data;
     int Len;
};

the autoexp.data might look like:

auto_array<*> {
    children
    (
        #array
        (
            expr :      $e.Data[$i],
            size :      $e.Len
        )
    )
    preview
    (
        #(
            "[", $e.Len , "](",
            #array
            (
                expr :  $e.Data[$i],
                size :  $e.Len
            ),
            ")"
        )
    )
}

KindDragon reports that Visual Studio 2012 uses a new file format: natvis