diff --git a/man/revealjs_presentation.Rd b/man/revealjs_presentation.Rd
index ce1e0c6..2741765 100644
--- a/man/revealjs_presentation.Rd
+++ b/man/revealjs_presentation.Rd
@@ -249,6 +249,22 @@
 \code{.Rmd} source file without rendering it.
 }
 
+\subsection{Vertical content centering}{
+
+Slides with little content look lost when everything is glued below the
+title bar, while packed slides must start at the top. reveal.js' own
+\code{center} option cannot express this -- it also vertically centers the
+headings. Instead, the body content of each slide (everything after the
+heading block except speaker notes) is grouped and, whenever there is
+free space, centered in the area between the heading and the footer:
+slides that are too packed simply start directly below the heading and
+overflow downwards, exactly as before. Centered content never reaches
+into the footer; content too tall to fit above it may, as it always
+could. Heading-only section-divider slides keep their own centered-title
+layout. No configuration is needed and nothing changes about how slides
+are authored.
+}
+
 \subsection{Chapter numbering}{
 
 Like in the old Google Docs slide workflow, chapter headings (\verb{#}) are