Anytime you need to display a piece of content—like an image with an optional caption, consider using a <figure>.
Use the included .figure, .figure-img and .figure-caption classes to provide some baseline styles for the HTML5 <figure> and <figcaption> elements. Images in figures have no explicit size, so be sure to add the .img-fluid class to your <img> to make it responsive.
Aligning the figure’s caption is easy with our text utilities.
CSS
Sass variables
$figure-caption-font-size: $small-font-size;
$figure-caption-color: var(--#{$prefix}secondary-color);