JSFiddle - React, Tailwind, and code Playground

HTML

<div id="parent">
    <!-- the anonymous div which I want to hide and display by clicking on div#child-2 -->
    <div>
        <div id="Container1">
            <span>Container1</span>
        </div>
    </div>
    <div onclick="appear()" id="child-2">
        <div id="child-of-child">child-of-child</div>
    </div>
</div>

CSS

div#parent div:first-child div:first-child {
    display: none;
}

JavaScript

function appear() {
    document.getElementById("Container1").style.display="block";
}