JSFiddle - React, Tailwind, and code Playground

HTML

<div class="header">
    <form>
        <label>Label</label>
        <div id="w"><input type="text" /></div>
        <input type="submit" value="ok" />
    </form>
</div>

CSS

.header {
    width: 100%;
}
form {
    width: 50%;
    background-color: lightgray;
    display: table;
}
#w{
    background:black;
}
input[type=submit], label,#w {
    display: table-cell;
}
input[type=text] {
    width: 100%;
    border:1px solid grey;
    padding:0;
    margin:0;
}