diff --git a/module2/exo4/exercice.ipynb b/module2/exo4/exercice.ipynb
index 0bbbe371b01e359e381e43239412d77bf53fb1fb..458afe6e211821210e8ecadde407b9a8fb30d45b 100644
--- a/module2/exo4/exercice.ipynb
+++ b/module2/exo4/exercice.ipynb
@@ -1,5 +1,78 @@
 {
- "cells": [],
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "# Journal de bord"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## 16/01/2021\n",
+    "\n",
+    "Pour ajouter des équations dans des cellules Markdown, mettre les éléments entre des `$ $`.\\\n",
+    "Par exemple:\\\n",
+    "`$\\pi$` → $\\pi$\\\n",
+    "`$X^2 + Y_2$` → $X^2 + Y_2$\n",
+    "\n",
+    "Pour plus de détails, voir le [wikibook sur LaTeX](https://en.wikibooks.org/wiki/LaTeX/Mathematics)."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## 17/01/2021\n",
+    "Pour la fonction histogramme plt.hist(), bins = permet de fixer le nombre de barres, pas la largeur de l'histogramme.\\\n",
+    "Une façon de contourner ça:\\\n",
+    "`\n",
+    "binwidth = 2\n",
+    "plt.hist(x, bins=np.arange(min(x), max(x) + binwidth, binwidth\n",
+    "`"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Pour rajouter une grille sur un graphe :\\\n",
+    "`\n",
+    "plt.grid(b= True, which = 'major', axis = 'both', linestyle = '--')\n",
+    "`\\\n",
+    "'--' permet d'avoir des pointillés.\\\n",
+    "Pour plus de détails, voir [Matplotlib grid](https://matplotlib.org/3.1.1/api/_as_gen/matplotlib.pyplot.grid.html)."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Pour définir les titres des axes et du graphe:\\\n",
+    "`\n",
+    "plt.xlabel(\"Year\")\n",
+    "plt.ylabel(\"Salary\")\n",
+    "plt.title(\"Example of Histogram Plot\")\n",
+    "`\\\n",
+    "\n",
+    "`\n",
+    "plt.show()\n",
+    "` pour afficher le graphe (pas nécessaire dans un notebook).\n",
+    "\n",
+    "Pour définir les clouleurs des barres et de leur contour:\\\n",
+    "`plt.hist(x,  color='b', edgecolor='black')`"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  }
+ ],
  "metadata": {
   "kernelspec": {
    "display_name": "Python 3",
@@ -16,10 +89,9 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.6.3"
+   "version": "3.6.4"
   }
  },
  "nbformat": 4,
  "nbformat_minor": 2
 }
-