With Polishing your typography with line height units Jen Simmons is putting a spotlight on the overlooked lh unit. It makes a big difference!
Line height units give us a direct way to tie any size in our layout to the vertical rhythm of the text.
I like to apply it in a flow css class to set the space between direct siblings:
.flow > * + * {
margin-block-start: 1em; /* fallback for browsers not supporting the lh unit */
margin-block-start: 1lh;
}