Optgroup
HTML
<select>
<optgroup label="MeasurementGroup">
<option value="Service Type Block ">Volvo</option>
<option value="saab">Saab</option>
</optgroup>
<optgroup label="Section">
<option value="mercedes">Mercedes</option>
<optgroup label=" Audi">
<option value="a8"> A8</option>
<option value="a7"> A7</option>
</optgroup>
</optgroup>
</select>