JSFiddle - React, Tailwind, and code Playground

HTML

<div class="parent">
    <div class="child">
        <textarea></textarea>
    </div>
</div>

CSS

.parent{
    position:absolute;
    height:200px;
    width:400px;
    background-color:blue;
}

.child{
    position:absolute;
    bottom:2px;
    left:2px;
    right:2px;
   -moz-box-sizing:border-box;
}
.child textarea{
    width:100%;
    height:30px;
    box-sizing:border-box;
    -moz-box-sizing:border-box;
    -webkit-box-sizing:border-box;
}