diff --git a/tutorial/docs/04-physics-list.ipynb b/tutorial/docs/04-physics-list.ipynb
index 60b3438..22e2987 100644
--- a/tutorial/docs/04-physics-list.ipynb
+++ b/tutorial/docs/04-physics-list.ipynb
@@ -78,7 +78,7 @@
     "    detector = World(),               # should be the default\n",
     "    generator = G4JLGunGenerator(),   # should be the default\n",
     "    physics_type = FTFP_BERT\n",
-    ")"
+    ");"
    ]
   },
   {
@@ -94,7 +94,11 @@
   {
    "cell_type": "code",
    "execution_count": null,
-   "metadata": {},
+   "metadata": {
+    "tags": [
+     "scroll-output"
+    ]
+   },
    "outputs": [],
    "source": [
     "DumpList(app.physics)"
@@ -131,8 +135,8 @@
     "struct MyPhysicsList <: G4VUserPhysicsList\n",
     "    function MyPhysicsList(verbose)\n",
     "        pl = G4VModularPhysicsList()\n",
-    "        RegisterPhysics(pl, move!(G4EmStandardPhysics(verbose)))\n",
-    "        RegisterPhysics(pl, move!(G4OpticalPhysics(verbose)))\n",
+    "        RegisterPhysics(pl, move!(G4EmStandardPhysics(verbose)))  # make sure that the ownership is correctly transferred\n",
+    "        RegisterPhysics(pl, move!(G4OpticalPhysics(verbose)))     # by calling move!()\n",
     "        return pl\n",
     "    end \n",
     "end"
@@ -156,7 +160,11 @@
   {
    "cell_type": "code",
    "execution_count": null,
-   "metadata": {},
+   "metadata": {
+    "tags": [
+     "scroll-output"
+    ]
+   },
    "outputs": [],
    "source": [
     "DumpList(app.physics)"