JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html>
<head>
	
	<title>Layers Control Tutorial - Leaflet</title>

	<meta charset="utf-8" />
	<meta name="viewport" content="width=device-width, initial-scale=1.0">
	
	<link rel="shortcut icon" type="image/x-icon" href="docs/images/favicon.ico" />

    <link rel="stylesheet" href="https://unpkg.com/[email protected]/dist/leaflet.css" integrity="sha512-Rksm5RenBEKSKFjgI3a41vrjkw4EVPlJ3+OiI65vTjIdo9brlAacEuKOiQ5OFh7cOI1bkDwLqdLw3Zg0cRJAAQ==" crossorigin=""/>
    <script src="https://unpkg.com/[email protected]/dist/leaflet.js" integrity="sha512-/Nsx9X4HebavoBvEBuyp3I7od5tA0UzAxs+j83KgC8PU0kgB4XiK4Lfe4y4cgBtaRJQEIFCW+oC506aPT2L1zw==" crossorigin=""></script>


	<style>
		html, body {
			height: 100%;
			margin: 0;
		}
		#map {
			width: 100%;
			height: 100%;
		}
	</style>

	
</head>
<body>

<div id='map'></div>

</body>
</html>

CSS

.leaflet-control-layers-toggle {
    background-image: url(https://image.flaticon.com/icons/png/512/126/126472.png) !important;
    background-size: 26px;
}
.leaflet-control-layers {
    box-shadow: none !important;
    border-radius: 0px !important;
}

JavaScript

var cities = L.layerGroup();

	L.marker([39.61, -105.02]).bindPopup('This is Littleton, CO.').addTo(cities),
	L.marker([39.74, -104.99]).bindPopup('This is Denver, CO.').addTo(cities),
	L.marker([39.73, -104.8]).bindPopup('This is Aurora, CO.').addTo(cities),
	L.marker([39.77, -105.23]).bindPopup('This is Golden, CO.').addTo(cities);


	var mbAttr = 'Map data &copy; <a href="https://www.openstreetmap.org/">OpenStreetMap</a> contributors, ' +
			'<a href="https://creativecommons.org/licenses/by-sa/2.0/">CC-BY-SA</a>, ' +
			'Imagery © <a href="https://www.mapbox.com/">Mapbox</a>',
		mbUrl = 'https://api.tiles.mapbox.com/v4/{id}/{z}/{x}/{y}.png?access_token=pk.eyJ1IjoibWFwYm94IiwiYSI6ImNpejY4NXVycTA2emYycXBndHRqcmZ3N3gifQ.rJcFIG214AriISLbB6B5aw';

	var grayscale   = L.tileLayer(mbUrl, {id: 'mapbox.light', attribution: mbAttr}),
		streets  = L.tileLayer(mbUrl, {id: 'mapbox.streets',   attribution: mbAttr});

	var map = L.map('map', {
		center: [39.73, -104.99],
		zoom: 10,
		layers: [grayscale, cities]
	});

	var baseLayers = {
		"Grayscale": grayscale,
		"Streets": streets
	};

	var overlays = {
		"Cities": cities
	};

	L.control.layers(baseLayers, overlays).addTo(map);