diff --git a/docs/source/user_guide/structuredata/API_start.ipynb b/docs/source/user_guide/structuredata/API_start.ipynb
index 6010fd8..6b29fa4 100644
--- a/docs/source/user_guide/structuredata/API_start.ipynb
+++ b/docs/source/user_guide/structuredata/API_start.ipynb
@@ -4,7 +4,30 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "# The StructureData object"
+    "# <a id='toc1_'></a>[The StructureData object](#toc0_)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "**Table of contents**<a id='toc0_'></a>    \n",
+    "- [The StructureData object](#toc1_)    \n",
+    "  - [Initialization of a StructureData instance](#toc1_1_)    \n",
+    "    - [How to define the properties](#toc1_1_1_)    \n",
+    "    - [Inspect the supported and stored properties from the StructureData instance:](#toc1_1_2_)    \n",
+    "      - [Missing: access the supported property from the class object](#toc1_1_2_1_)    \n",
+    "    - [The immutability of the StructureData instance](#toc1_1_3_)    \n",
+    "    - [How to get kinds](#toc1_1_4_)    \n",
+    "\n",
+    "<!-- vscode-jupyter-toc-config\n",
+    "\tnumbering=false\n",
+    "\tanchor=true\n",
+    "\tflat=false\n",
+    "\tminLevel=1\n",
+    "\tmaxLevel=6\n",
+    "\t/vscode-jupyter-toc-config -->\n",
+    "<!-- THIS CELL WILL BE REPLACED ON TOC UPDATE. DO NOT WRITE YOUR TEXT IN THIS CELL -->"
    ]
   },
   {
@@ -38,27 +61,16 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 1,
+   "execution_count": 16,
    "metadata": {},
    "outputs": [
-    {
-     "name": "stdout",
-     "output_type": "stream",
-     "text": [
-      "\u001b[93m\u001b[1mWarning\u001b[0m: \u001b[22mYou are currently using a post release development version of AiiDA: 2.4.0.post0\u001b[0m\n",
-      "\u001b[93m\u001b[1mWarning\u001b[0m: \u001b[22mBe aware that this is not recommended for production and is not officially supported.\u001b[0m\n",
-      "\u001b[93m\u001b[1mWarning\u001b[0m: \u001b[22mDatabases used with this version may not be compatible with future releases of AiiDA\u001b[0m\n",
-      "\u001b[93m\u001b[1mWarning\u001b[0m: \u001b[22mas you might not be able to automatically migrate your data.\n",
-      "\u001b[0m\n"
-     ]
-    },
     {
      "data": {
       "text/plain": [
        "Profile<uuid='827a33dde1bc4d498af8e022f9e9dece' name='mikibonacci'>"
       ]
      },
-     "execution_count": 1,
+     "execution_count": 16,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -100,7 +112,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 2,
+   "execution_count": 17,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -121,7 +133,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 3,
+   "execution_count": 18,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -139,16 +151,16 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 4,
+   "execution_count": 19,
    "metadata": {},
    "outputs": [
     {
      "data": {
       "text/plain": [
-       "Mass(parent=<StructureData: uuid: d0f2b3b7-38e6-4193-a028-5f0f21bea03b (unstored)>, value=[6.941, 6.945], domain='intra-site', default_kind_threshold=0.001)"
+       "Mass(parent=<StructureData: uuid: 72047b25-c462-4737-b06a-e4274afbc105 (unstored)>, value=[6.941, 6.945], domain='intra-site', default_kind_threshold=0.001)"
       ]
      },
-     "execution_count": 4,
+     "execution_count": 19,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -159,7 +171,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 5,
+   "execution_count": 20,
    "metadata": {},
    "outputs": [
     {
@@ -168,7 +180,7 @@
        "[6.941, 6.945]"
       ]
      },
-     "execution_count": 5,
+     "execution_count": 20,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -179,7 +191,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 6,
+   "execution_count": 21,
    "metadata": {},
    "outputs": [
     {
@@ -188,7 +200,7 @@
        "'intra-site'"
       ]
      },
-     "execution_count": 6,
+     "execution_count": 21,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -206,7 +218,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 7,
+   "execution_count": 22,
    "metadata": {},
    "outputs": [
     {
@@ -215,7 +227,7 @@
        "{'value': [6.941, 6.945]}"
       ]
      },
-     "execution_count": 7,
+     "execution_count": 22,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -228,21 +240,21 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "### Inspect the supported and stored properties from the StructureData instance:"
+    "### <a id='toc1_1_2_'></a>[Inspect the supported and stored properties from the StructureData instance:](#toc0_)"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 8,
+   "execution_count": 23,
    "metadata": {},
    "outputs": [
     {
      "data": {
       "text/plain": [
-       "['positions', 'cell', 'pbc', 'mass', 'symbols', 'custom', 'charge']"
+       "['pbc', 'mass', 'custom', 'cell', 'symbols', 'charge', 'positions']"
       ]
      },
-     "execution_count": 8,
+     "execution_count": 23,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -253,16 +265,16 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 9,
+   "execution_count": 24,
    "metadata": {},
    "outputs": [
     {
      "data": {
       "text/plain": [
-       "['positions', 'cell', 'pbc', 'mass', 'symbols', 'charge']"
+       "['mass', 'cell', 'pbc', 'symbols', 'charge', 'positions']"
       ]
      },
-     "execution_count": 9,
+     "execution_count": 24,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -275,7 +287,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "#### Missing: access the supported property from the class object\n",
+    "#### <a id='toc1_1_2_1_'></a>[Missing: access the supported property from the class object](#toc0_)\n",
     "\n",
     "```python\n",
     "In [1]: StructureData.get_supported_properties()\n",
@@ -287,7 +299,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "### The immutability of the StructureData instance"
+    "### <a id='toc1_1_3_'></a>[The immutability of the StructureData instance](#toc0_)"
    ]
   },
   {
@@ -303,7 +315,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 10,
+   "execution_count": 25,
    "metadata": {},
    "outputs": [
     {
@@ -317,7 +329,7 @@
        " 'charge': {'value': [1, 0]}}"
       ]
      },
-     "execution_count": 10,
+     "execution_count": 25,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -329,7 +341,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 11,
+   "execution_count": 26,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -338,7 +350,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 12,
+   "execution_count": 27,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -347,7 +359,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": 13,
+   "execution_count": 28,
    "metadata": {},
    "outputs": [
     {
@@ -356,7 +368,7 @@
        "[6.941, 6.941]"
       ]
      },
-     "execution_count": 13,
+     "execution_count": 28,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -369,14 +381,14 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "### How to get kinds\n",
+    "### <a id='toc1_1_4_'></a>[How to get kinds](#toc0_)\n",
     "\n",
     "It is possible to get a list of kinds using the `get_kinds` method. This will generate the corresponding predicted kinds for all the properties (the \"intra-site\" ones) and then generate the list of global different kinds. \n"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 16,
+   "execution_count": 29,
    "metadata": {},
    "outputs": [
     {
@@ -395,7 +407,7 @@
        " {'mass': [6.9415, 6.945500000000001], 'charge': [1.1250000000000002, 0.225]})"
       ]
      },
-     "execution_count": 16,
+     "execution_count": 29,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -408,12 +420,15 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
+    "As you can see, basically the value of a property is not the starting value choosen, and this is a PROBLEM: we have TOFIX this, especially in case in which the value is zero. \n",
+    "The issue is that we are using a middle-point representative value.\n",
+    "\n",
     "Kinds are determined using, for each property, a given threshold. There is a default threshold:"
    ]
   },
   {
    "cell_type": "code",
-   "execution_count": 17,
+   "execution_count": 30,
    "metadata": {},
    "outputs": [
     {
@@ -422,7 +437,7 @@
        "0.001"
       ]
      },
-     "execution_count": 17,
+     "execution_count": 30,
      "metadata": {},
      "output_type": "execute_result"
     }
@@ -441,6 +456,11 @@
     "structure.get_kinds(thr={\"mass\":0.1})\n",
     "```"
    ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": []
   }
  ],
  "metadata": {