diff --git a/src/lib/iter-source.hpp b/src/lib/iter-source.hpp
index 2444d8aa1..28429cd5d 100644
--- a/src/lib/iter-source.hpp
+++ b/src/lib/iter-source.hpp
@@ -261,6 +261,10 @@ namespace lib {
       WrappedLumieraIter (IT&& orig)
         : src_(forward<IT>(orig))
         { }
+      
+      
+    protected:
+      IT& wrappedIter() { return src_; }
     };
   
   
diff --git a/src/lib/iter-tree-explorer.hpp b/src/lib/iter-tree-explorer.hpp
index 81508c7ab..95bb7bdb9 100644
--- a/src/lib/iter-tree-explorer.hpp
+++ b/src/lib/iter-tree-explorer.hpp
@@ -111,6 +111,8 @@ namespace lib {
   using std::function;
   using util::isnil;
   
+  namespace error = lumiera::error;
+  
   namespace iter_explorer {
     
     template<class CON>
@@ -434,7 +436,7 @@ namespace lib {
   
   
   
-  namespace iter_explorer {
+  namespace iter_explorer { // Implementation of Iterator decorating layers...
     
     /**
      * @internal Base of pipe processing decorator chain.
@@ -733,7 +735,38 @@ namespace lib {
               ++srcIter();
           }
       };
-  }
+    
+    
+    class ChildExpandableSource
+      {
+      protected:
+         ~ChildExpandableSource() { }    ///< @note mix-in interface, not meant to handle objects
+      public:
+          virtual void expandChildren()  =0;
+      };
+    
+    /**
+     * @todo WIP
+     */
+    template<class SRC>
+    class PackagedTreeExplorerSource
+      : public WrappedLumieraIter<SRC>
+      , public ChildExpandableSource
+      {
+        using Parent = WrappedLumieraIter<SRC>;
+        
+      public:
+        using Parent::Parent;
+        
+        virtual void
+        expandChildren()  override
+          {
+            Parent::wrappedIter().expandChildren();
+          }
+      };
+    
+  }//(End)Iterator decorating layer implementation
+  
   
   
   
@@ -746,15 +779,35 @@ namespace lib {
     : IterSource<VAL>::iterator
     {
       
-      //////TODO clarify allowed ctors
+      IterExploreSource()  =default;
+      // inherited default copy operations
+      
       
       void
       expandChildren()
         {
-          UNIMPLEMENTED ("how to phone home...");
+          using Expandable = iter_explorer::ChildExpandableSource;
+          
+          if (not this->source())
+            throw error::State ("operating on a disabled default constructed TreeExplorer"
+                               ,error::LUMIERA_ERROR_BOTTOM_VALUE);
+          
+          auto source = this->source().get();
+          dynamic_cast<Expandable*> (source)->expandChildren();
         }
       
+      
     private:
+      template<class SRC>
+      friend class TreeExplorer;
+      
+      template<class IT>
+      IterExploreSource (IT&& opaqueSrcPipeline)
+        : IterSource<VAL>::iterator {
+            IterSource<VAL>::build (
+              new iter_explorer::PackagedTreeExplorerSource<IT> {
+                move (opaqueSrcPipeline)})}
+      { }
     };
   
   /**
@@ -879,7 +932,7 @@ namespace lib {
       IterExploreSource<value_type>
       asIterSource()
         {
-          UNIMPLEMENTED ("wrap into IterSource");       
+          return IterExploreSource<value_type> {move(*this)};
         }
       
       
diff --git a/tests/library/iter-tree-explorer-test.cpp b/tests/library/iter-tree-explorer-test.cpp
index f1d7a4362..a6c330d8d 100644
--- a/tests/library/iter-tree-explorer-test.cpp
+++ b/tests/library/iter-tree-explorer-test.cpp
@@ -759,6 +759,13 @@ namespace test{
           cout << materialise(exploreIter) << endl;
           
           CHECK (isnil (sequence));
+          CHECK (38 == *sequence);
+//          CHECK (38 == *exploreIter);
+          ++exploreIter;
+          exploreIter.expandChildren();
+          cout << materialise(exploreIter) << endl;
+#if false /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #888
+#endif    /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #888
         }
       
       
diff --git a/wiki/thinkPad.ichthyo.mm b/wiki/thinkPad.ichthyo.mm
index 2c95fb1f9..4cbf4d81f 100644
--- a/wiki/thinkPad.ichthyo.mm
+++ b/wiki/thinkPad.ichthyo.mm
@@ -6030,12 +6030,86 @@
 <icon BUILTIN="flag-yellow"/>
 <node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1512621268527" ID="ID_1388034155" MODIFIED="1512621305821" TEXT="wie bauen?">
 <icon BUILTIN="help"/>
+<node CREATED="1512711450864" ID="ID_1595268563" MODIFIED="1512711455248" TEXT="sollte simpel sein"/>
+<node CREATED="1512711430770" ID="ID_217126119" MODIFIED="1512711446628" TEXT="mit builder-Funktion die Baseclass initialisieren"/>
 </node>
 <node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1512621274166" ID="ID_1452751365" MODIFIED="1512621301316" TEXT="wie expand() an die Quelle weitergeben?">
 <icon BUILTIN="help"/>
+<node CREATED="1512711382889" ID="ID_1913647489" MODIFIED="1512711393299" TEXT="mu&#xdf; virtuelle methode sein"/>
+<node CREATED="1512711396279" ID="ID_633403108" MODIFIED="1512769358637" TEXT="also: mu&#xdf; IterSource erweitern">
+<arrowlink COLOR="#b92b64" DESTINATION="ID_1665958887" ENDARROW="Default" ENDINCLINATION="65;-99;" ID="Arrow_ID_1257583135" STARTARROW="None" STARTINCLINATION="-371;-34;"/>
+</node>
+<node CREATED="1512711404526" ID="ID_17184885" MODIFIED="1512711414688" TEXT="IterSource steckt im shared_ptr"/>
+<node CREATED="1512711415324" ID="ID_1951957730" MODIFIED="1512711423975" TEXT="also mu&#xdf; Front-End einen downcast machen"/>
+</node>
+<node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1512711462926" ID="ID_1665958887" MODIFIED="1512769358637" TEXT="IterSource erweitern">
+<linktarget COLOR="#b92b64" DESTINATION="ID_1665958887" ENDARROW="Default" ENDINCLINATION="65;-99;" ID="Arrow_ID_1257583135" SOURCE="ID_633403108" STARTARROW="None" STARTINCLINATION="-371;-34;"/>
+<icon BUILTIN="flag-yellow"/>
+<node COLOR="#b60303" CREATED="1512711475196" HGAP="15" ID="ID_899953833" MODIFIED="1512769566817" TEXT="Diamond of Death ?!!" VSHIFT="23">
+<icon BUILTIN="messagebox_warning"/>
+</node>
+<node COLOR="#338800" CREATED="1512711573727" ID="ID_1346721743" MODIFIED="1512769144693" TEXT="TODO: virtuelle inheritance nachlesen">
+<icon BUILTIN="button_ok"/>
+<node CREATED="1512769100530" ID="ID_547968053" MODIFIED="1512769116100" TEXT="vitual mu&#xdf; direkt unter der Basis erfolgen"/>
+<node CREATED="1512769116952" ID="ID_1359676759" MODIFIED="1512769124770" TEXT="virtual mu&#xdf; dort in allen Zweigen verwendet werden"/>
+<node CREATED="1512769133350" ID="ID_609049064" MODIFIED="1512769142944" TEXT="andernfalles bekommen wir mehrere Sub-Objekte der Basisklasse"/>
+</node>
+<node CREATED="1512711613841" ID="ID_1594826715" MODIFIED="1512711635619" STYLE="fork" TEXT="Kosten? zus&#xe4;tzlicher VTable-Pointer?">
+<node CREATED="1512711638574" ID="ID_1769096857" MODIFIED="1512769458120" TEXT="k&#xf6;nnte verschmerzbar sein">
+<icon BUILTIN="help"/>
+</node>
+<node CREATED="1512769160218" ID="ID_155388893" MODIFIED="1512769462006" TEXT="Kosten kommen vom Memory-Layout">
+<icon BUILTIN="info"/>
+</node>
+<node CREATED="1512769179503" ID="ID_1053011981" MODIFIED="1512769198300">
+<richcontent TYPE="NODE"><html>
+  <head>
+    
+  </head>
+  <body>
+    <p>
+      <i>jeder</i>&#160;Zugriff auf ein Sub-Objekt mu&#223; durch eine VTable
+    </p>
+  </body>
+</html>
+</richcontent>
+</node>
+<node CREATED="1512769199597" ID="ID_1928524017" MODIFIED="1512769227486">
+<richcontent TYPE="NODE"><html>
+  <head>
+    
+  </head>
+  <body>
+    <p>
+      Stichwort: <b>virtual base offset</b>
+    </p>
+  </body>
+</html>
+</richcontent>
+</node>
+<node COLOR="#5229a2" CREATED="1512769231648" ID="ID_925551162" LINK="http://web.archive.org/web/20160413064252/http://www.phpcompiler.org/articles/virtualinheritance.html" MODIFIED="1512769289609" TEXT="Beschreibung der GCC-Implementierung">
+<font ITALIC="true" NAME="SansSerif" SIZE="14"/>
+<icon BUILTIN="idea"/>
 </node>
 </node>
-<node COLOR="#338800" CREATED="1512621185490" ID="ID_1611878074" MODIFIED="1512706124361" TEXT="Probleme">
+<node CREATED="1512711586005" ID="ID_652398650" MODIFIED="1512769369479" TEXT="vielleicht kein Problem, da wir explizit casten">
+<node CREATED="1512769376605" ID="ID_1401491527" MODIFIED="1512769512216" TEXT="ja, workaround">
+<arrowlink COLOR="#7c89a1" DESTINATION="ID_813779439" ENDARROW="Default" ENDINCLINATION="178;-25;" ID="Arrow_ID_1765195063" STARTARROW="None" STARTINCLINATION="23;85;"/>
+<icon BUILTIN="idea"/>
+</node>
+<node CREATED="1512769383980" ID="ID_415336941" MODIFIED="1512769397102" TEXT="den Zusammenhang nicht im Interface ausdr&#xfc;cken"/>
+<node CREATED="1512769398050" ID="ID_1821068883" MODIFIED="1512769409404" TEXT="zusatz-Feature &quot;extendChildren&quot; in separates Interface"/>
+</node>
+<node COLOR="#2b3cb9" CREATED="1512769068942" ID="ID_1398747892" LINK="https://stackoverflow.com/questions/47722508/cost-of-virtual-inheritance-from-an-interface" MODIFIED="1512769090329" TEXT="Frage auf Stackoverflow gepostet">
+<icon BUILTIN="info"/>
+</node>
+<node CREATED="1512769478607" HGAP="-17" ID="ID_813779439" MODIFIED="1512769512216" TEXT="setze den Workaround um" VSHIFT="28">
+<linktarget COLOR="#7c89a1" DESTINATION="ID_813779439" ENDARROW="Default" ENDINCLINATION="178;-25;" ID="Arrow_ID_1765195063" SOURCE="ID_1401491527" STARTARROW="None" STARTINCLINATION="23;85;"/>
+<icon BUILTIN="yes"/>
+</node>
+</node>
+</node>
+<node COLOR="#338800" CREATED="1512621185490" ID="ID_1611878074" MODIFIED="1512706690893" TEXT="Probleme">
 <icon BUILTIN="button_ok"/>
 <node CREATED="1512621202688" ID="ID_57740660" MODIFIED="1512706113620" TEXT="durchreichen der Basis-Konstruktoren">
 <icon BUILTIN="info"/>
@@ -6544,6 +6618,9 @@
 </html>
 </richcontent>
 <icon BUILTIN="messagebox_warning"/>
+<node CREATED="1512711333823" ID="ID_1629518942" MODIFIED="1512711345303" TEXT="Idee: deepCopy bieten">
+<icon BUILTIN="idea"/>
+</node>
 </node>
 </node>
 <node BACKGROUND_COLOR="#eee5c3" COLOR="#990000" CREATED="1510969031379" ID="ID_1327871737" MODIFIED="1510969042972" TEXT="verify_depthFirstExploration();">