Each morph (except for the world itself) is owned by exactly one other morph.
You can see the owner of a morph by asking for its owner property, like this:
$morph('SmallEllipse').owner
which gives us a string. If the owner is null,then the owner is the world itself.
The string doesn't tell us much., but fortunately you can get a morph to show itself. Try cmd-d on:
$morph('SmallEllipse').owner.show()
which shows little red corners on the small rectangle
you can also do:
$morph('SmallEllipse').owner.owner.show()
You can also get the owner chain of a morph by continually cmd-clicking on it; this will show the halos of each owner in its chain, until it's done