如何使用Twig将较小的模板分组并渲染到一个文件中

I just started using Twig and have been reading up on it. I don't want to create a whole file for a small template such as:

<tr>
    <td>{{ firstname }}</td>
    <td>{{ lastname }}</td>
</tr>

I would like to group my templates into one file and be able to render a specific snippet/template from the file. Obviously I could easily do this by using pure PHP but I want to keep my HTML separate from my PHP because it just looks a lot cleaner. I might look into saving the templates into a database but that just seems like a lot of work. Any help is appreciated.