title: How do I insert multiple rows inside a row on material ui
body: <p>I'm trying to add multiple rows inside a row of my table
  See it here:</p>
  
  <p><a href="https://i.stack.imgur.com/reNBN.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/reNBN.png" alt="enter image description here"></a></p>
  
  <p>And I don't know why my 4 last cells are into the TableHead "Langues".</p>
  
  <p>Here's my code :</p>
  
  <pre><code>&lt;Paper className={classes.root}&gt;
              &lt;Table className={classes.table}&gt;
                &lt;TableHead&gt;
                  &lt;TableRow&gt;
                    &lt;TableCell numeric&gt;id&lt;/TableCell&gt;
                    &lt;TableCell&gt;Actif&lt;/TableCell&gt;
                    &lt;TableCell&gt;Payant&lt;/TableCell&gt;
                    &lt;TableCell&gt;Langues&lt;/TableCell&gt;
                    &lt;TableCell&gt;Noms&lt;/TableCell&gt;
                    &lt;TableCell&gt;Image univers débloqué&lt;/TableCell&gt;
                    &lt;TableCell&gt;Image univers bloqué&lt;/TableCell&gt;
                  &lt;/TableRow&gt;
                &lt;/TableHead&gt;
                &lt;TableBody&gt;
                {
                  this.state.universes.map((item, i) =&gt; {
                    return (
                      &lt;TableRow key={i}&gt;
                      &lt;TableCell numeric&gt;{item.id}&lt;/TableCell&gt;
                      &lt;TableCell&gt;{item.active?"Oui":"Non"}&lt;/TableCell&gt;
                      &lt;TableCell&gt;{item.free?"Non":"Oui"}&lt;/TableCell&gt;
                          {
                            item.Langs.map((item, y) =&gt; {
                              return (
                                &lt;TableRow key={y}&gt;
                                  &lt;TableCell&gt;{item.lang}&lt;/TableCell&gt;
                                  &lt;TableCell&gt;{item.name}&lt;/TableCell&gt;
                                  &lt;TableCell&gt;&lt;img height="50" src={item.activeImage}/&gt;&lt;/TableCell&gt;
                                  &lt;TableCell&gt;&lt;img height="50" src={item.disabledImage}/&gt;&lt;/TableCell&gt;
                                &lt;/TableRow&gt;
                              )
                            })
                          }
                      &lt;/TableRow&gt;
                    )
                  })
                }
              &lt;/TableBody&gt;
            &lt;/Table&gt;
          &lt;/Paper&gt;
  </code></pre>
  
  <p>Does someone can help me ?</p>