diff --git a/dune/solvers/iterationsteps/multigridstep.hh b/dune/solvers/iterationsteps/multigridstep.hh
index d315df2c797e0387d16f6a94a0c2951a49e645c4..baa7c1a3e7357a42a41b4bb1b6df7e620808a810 100644
--- a/dune/solvers/iterationsteps/multigridstep.hh
+++ b/dune/solvers/iterationsteps/multigridstep.hh
@@ -271,6 +271,10 @@
         std::vector<BitVectorType*> ignoreNodesHierarchy_;
 
     public:
+        /**  \brief! hierarchy of solution/correction vectors.
+          *
+          *  on the fine level it contains the iterate, whereas on the coarse levels the corresponding corrections
+          */
         std::vector<Dune::shared_ptr<VectorType> > xHierarchy_;
 
         std::vector<VectorType> rhsHierarchy_;
@@ -285,7 +289,6 @@
         typedef std::map<std::size_t, Dune::shared_ptr<LinearIterationStep<MatrixType, VectorType> > > SmootherCache;
         SmootherCache levelWiseSmoothers_;
 
-
         bool preprocessCalled;
     };