wp-calypso/apps/notifications/src/panel/boot/stylesheets/shared/animations.scss

.wpnc__single-view {
	animation-name: wpnc_fadeIn;
	animation-duration: 0.2s;
	animation-timing-function: ease-in;
}

@keyframes wpnc_fadeIn {
	from {
		opacity: 0;
	}
	to {
		opacity: 1;
	}
}