JSFiddle - React, Tailwind, and code Playground

HTML

<table class="Main">
    <tr>
        <td>This</td>
        <td>is</td>
        <td>first</td>
        <td>child</td>
    </tr>
    <tr>
        <td>A</td>
        <td>Regular</td>
        <td>Row</td>
        <td>
            <table>
                <tr>
                    <td>Nested</td>
                    <td>first</td>
                    <td>child</td>
                </tr>
                <tr>
                    <td>Nested</td>
                    <td>Table</td>
                    <td>Row</td>
                </tr>
            </table>
        </td>        
    </tr>
</table>

CSS

.Main table
{
	width: 100%;
	height: 100%;
	margin: 0px;
	padding: 0px;
}

.Main > tbody > tr:first-child td
{
	background-color: blue;
	text-align: center;
	border-width: 0px 0px 1px 1px;
	font-family: Arial;
	font-weight: bold;
	color: white;
}

.Main td
{
    border: 1px solid black;
	text-align: center;
	font-family: Arial;
	color: black;
}

.Main table table td
{
    border: 1px solid black;
	text-align: center;
	font-family: Arial;
	color: black;
}