First, you can no graph ascendants of your object. Say you have a reference, and you want to know the graph pointing to that reference. You can do it now:

class A; end
a = A.new
struct = {  ne => [], :two => [a] }

grapher = ObjectGraph.new(:ascendants => true)
grapher.graph(a)
puts grapher

Which will produce this graph:

You can also see differences in graphs. Say you want to know what happens to your graph after performing some action. Just pass a block to the graph method, and ObjectGraph will diff the two trees. Green boxes are new objects, pink boxes are one that went away, and red arrows are references that were destroyed.

class A; end
struct = {  ne => [], :two => [A.new]}

grapher = ObjectGraph.new
grapher.graph(struct) do |s|
  s[:one] << A.new
  s[:two].pop
end
puts grapher