Yes, a table can be embedded inside a cell in another table.
For example:
<table>
<tr>
<td>this is the first cell of the outer table</td>
<td>this is the second cell of the outer table,with the inner table embedded in it
<table>
<tr>
<td>this is the first cell of the inner table</td>
<td>this is the second cell of the inner table</td>
</tr>
</table>
</td>
</tr>
</table>