Margin

Class	Properties
.m-0	margin: 0
.m-05	margin: 0.125rem
.m-1	margin: 0.25rem
.m-4	margin: 1rem
.m-8	margin: 2rem
.m-auto	margin: auto

Directional: .mx-*, .my-*, .mt-*, .mr-*, .mb-*, .ml-*

<div class="m-4">All sides</div>
<div class="mx-auto my-8">Centered with vertical margin</div>
<div class="mt-4 mb-8">Top + bottom only</div>