JSFiddle - React, Tailwind, and code Playground

HTML

<div class="wrapper">
		<button> button
			<div class="container"></div>
		</button>
</div>

CSS

.wrapper {
	}

	button {
		color: red;

		position: relative;
		height: 100px;
	}

	.container {
		position: absolute;
		width: 10px;
		height: 100px;
		background: green;
    bottom: 0;
    transform: translateY(100%);
	}