JSFiddle - React, Tailwind, and code Playground

HTML

<div>
    
    <div class="container">
        
        <div class="one">
            <div class="one-inner"></div>
        </div>
                
        
                        
        <div class="three">
            <div class="three-inner"></div>
        </div>
        
    </div>
    
</div>

CSS

html, body {
    height: 100%;
}

.container {
    width: 80%;
    margin: 2em auto;
    height: 100%;
}

.one {
    background-color: whitesmoke;
    border: 1px solid gainsboro;
    width: 10%;
    min-width: 3em;
    padding: 1em;
    /* margin: 1em; */
    height: 10em;
}

.one, .two, .three {
    float: left;
}

.two {
    background-color: whitesmoke;
    border: 1px solid gainsboro;
    border-right: none;
    border-left: none;
    width: 40%;
    min-width: 5em;
    padding: 1em;
    /* margin: 1em; */
    height: 10em;
}

.three {
    background-color: whitesmoke;
    border: 1px solid gainsboro;
    width: 10%;
    min-width: 3em;
    padding: 1em;
   /*  margin: 1em; */
    height: 10em;
}

.one-inner {
    background: #ccc;
    border: 1px solid gray;
    display: block;
    width: 100%;
    height: 100%;
}

.two-inner {
    background-color: #cba;
    border: 1px solid gray;
    display: block;
    width: 100%;
    height: 100%;
}

.three-inner {
    background: #ca8;
    border: 1px solid gray;
    display: block;
    width: 100%;
    height: 100%;
}

.box {
    width: 15em;
    height: 10em;
    border: solid gray 0.15em;
    margin: 0.5em;
    display: inline-block;
    padding: 0.5em;
    border-radius: 0.5em;
}

.row {
    display: block;
    padding: 0 0.5em;
    margin: 0 auto;
}

.unit {
    min-width: 33em;
    width: 33em;
    margin: auto;
}

.float-right {
    float: right;
}

.float-left {
    float: left;
}

.margin-bottom-1em {
    margin-bottom: 1em;
}

.margin-top-1em {
    margin-top: 1em;
}

.margin-top-2em {
    margin-top: 2em;
}

.buttons {
    width: 30.6em;
    margin: 2em auto;
}

.button-fixed-width {
    width: 10em;
    display: inline-block;
}