diff --git a/techtree-manager/src/tree.rs b/techtree-manager/src/tree.rs
index 0574f73..f87873c 100644
--- a/techtree-manager/src/tree.rs
+++ b/techtree-manager/src/tree.rs
@@ -160,6 +160,16 @@ impl Tree {
         Subtree::new_for_element(self, element)
     }
 
+    pub fn iter_ultimate_elements<'a>(&'a self) -> impl Iterator<Item = ElementIndex> + 'a {
+        self.graph.node_indices().filter(|index| {
+            // If there are no incoming edges, then this is an ultimate element!
+            self.graph
+                .neighbors_directed(*index, petgraph::Direction::Incoming)
+                .next()
+                .is_none()
+        })
+    }
+
     pub fn to_dot(&self) -> String {
         let dot = petgraph::dot::Dot::with_attr_getters(
             &self.graph,
@@ -173,9 +183,16 @@ impl Tree {
             &|_g, (_, element)| element.to_dot_node_attributes(None),
         );
 
+        let ultimate_elements: Vec<_> = self
+            .iter_ultimate_elements()
+            .map(|idx| idx.index().to_string())
+            .collect();
+        let ultimate_element_list = ultimate_elements.join("; ");
+
         format!(
             r#"digraph {{
     ranksep=1.2
+    {{ rank=same; {ultimate_element_list}; }}
 {:?}
 }}
 "#,