diff --git a/cheuph/render/element.py b/cheuph/render/element.py
index 6d71c99..d55fd85 100644
--- a/cheuph/render/element.py
+++ b/cheuph/render/element.py
@@ -1,16 +1,145 @@
-from typing import Hashable, List
+import abc
+from typing import Hashable, List, Optional
 
+from .exceptions import ElementException, TreeException
 from .markup import AttributedText
 
 __all__ = ["Id", "Element", "ElementSupply", "RenderedElement"]
 
 Id = Hashable
 
-class Element:
-    pass
+class Element(abc.ABC):
+    def __init__(self,
+            id: Id,
+            parent_id: Optional[Id],
+            children: Optional[List[Element]],
+            ) -> None:
+        self._id = id
+        self._parent_id = id
 
-class ElementSupply:
-    pass
+        self._children = children
+
+    @property
+    def id(self) -> Id:
+        return self._id
+
+    @property
+    def parent_id(self) -> Id:
+        return self._parent_id
+
+    @property
+    def children(self) -> List[Element]:
+        if self._children is None:
+            raise ElementException("Element doesn't know its children")
+
+        return self._children
+
+    @children.setter
+    def children(self, children: List[Element]) -> None:
+        self._children = children
+
+    @abc.abstractmethod
+    def render(self,
+            depth: int,
+            highlighted: bool,
+            folded: bool,
+            ) -> RenderedElement:
+        pass
+
+class ElementSupply(abc.ABC):
+    @abc.abstractmethod
+    def get(self, element_id: Id) -> Element:
+        pass
+
+    @abc.abstractmethod
+    def get_parent_id(self, element_id: Id) -> Optional[Id]:
+        pass
+
+    def get_parent(self, element_id: Id) -> Optional[Element]:
+        parent_id = self.get_parent_id(element_id)
+
+        if parent_id is not None:
+            return self.get(parent_id)
+        else:
+            return None
+
+    @abc.abstractmethod
+    def get_children_ids(self, element_id: Id) -> List[Id]:
+        pass
+
+    def get_children(self, element_id: Id) -> List[Element]:
+        children_ids = self.get_children_ids(element_id)
+
+        children: List[Element] = []
+        for child_id in children_ids:
+            children.append(self.get(child_id))
+
+        return children
+
+    # There is not a clear-cut way to get the previous or next "sibling" of an
+    # element that is itself a child of the implicit root (None), since
+    # get_children() doesn't accept None in its element_id argument.
+    #
+    # Because of this, the get_previous_id() and get_next_id() functions are
+    # abstract (until I decide to change the signature of get_children(), that
+    # is :P).
+
+    @abc.abstractmethod
+    def get_previous_id(self, element_id: Id) -> Optional[Id]:
+        pass
+
+    def get_previous(self, element_id: Id) -> Optional[Element]:
+        previous_id = self.get_previous_id(element_id)
+
+        if previous_id is not None:
+            return self.get(previous_id)
+        else:
+            return None
+
+    @abc.abstractmethod
+    def get_next_id(self, element_id: Id) -> Optional[Id]:
+        pass
+
+    def get_next(self, element_id: Id) -> Optional[Element]:
+        next_id = self.get_next_id(element_id)
+
+        if next_id is not None:
+            return self.get(next_id)
+        else:
+            return None
+
+    def get_furthest_ancestor_id(self,
+            element_id: Id,
+            root_id: Optional[Id] = None,
+            ) -> Id:
+        current_id = element_id
+
+        while True:
+            parent_id = self.get_parent_id(current_id)
+
+            if parent_id == root_id:
+                return current_id
+            elif parent_id is None:
+                raise TreeException("Reached implicit root before hitting specified root")
+
+            current_id = parent_id
+
+    def get_furthest_ancestor(self,
+            element_id: Id,
+            root_id: Optional[Id] = None,
+            ) -> Element:
+        return self.get(self.get_furthest_ancestor_id(element_id,
+            root_id=root_id))
+
+    def get_tree(self, tree_id: Id) -> Element:
+        tree = self.get(tree_id)
+
+        children: List[Element] = []
+        for child_id in self.get_children_ids(tree_id):
+            children.append(self.get_tree(child_id))
+
+        tree.children = children
+        return tree
 
 class RenderedElement:
     def __init__(self,
diff --git a/cheuph/render/exceptions.py b/cheuph/render/exceptions.py
new file mode 100644
index 0000000..76c4edc
--- /dev/null
+++ b/cheuph/render/exceptions.py
@@ -0,0 +1,7 @@
+__all__ = ["ElementException", "TreeException"]
+
+class ElementException(Exception):
+    pass
+
+class TreeException(Exception):
+    pass
diff --git a/cheuph/render/tree_list.py b/cheuph/render/tree_list.py
index 8619572..ed9f06f 100644
--- a/cheuph/render/tree_list.py
+++ b/cheuph/render/tree_list.py
@@ -47,6 +47,10 @@ class TreeList:
     def lower_tree_id(self) -> Id:
         return self._lower_tree_id
 
+    def offset_by(self, offset: int) -> None:
+        self._upper_offset += offset
+        self._lower_offset += offset
+
     def _add_first_tree(self,
             tree: List[RenderedElement],
             anchor_id: Id