diff --git a/R/header_separate.R b/R/header_separate.R
new file mode 100644
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+++ b/R/header_separate.R
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+#' Separate table headers and add additional header rows based on grouping
+#'
+#' @description When you create a summary table for either model or basic
+#' summary stats in R, you usually end up having column names in the form of
+#' "a_mean", "a_sd", "b_mean" and "b_sd". This function streamlines the process
+#' of renaming these column names and adding extra header rows using
+#' `add_header_above`.
+#'
+#' @param kable_input Output of `knitr::kable()` with `format` specified
+#' @param sep A regular expression separator between groups. The default value
+#' is a regular expression that matches any sequence of non-alphanumeric values.
+#'
+#' @export
+header_separate <- function(kable_input, sep = "[^[:alnum:]]+") {
+  kable_format <- attr(kable_input, "format")
+  if (!kable_format %in% c("html", "latex")) {
+    warning("Please specify format in kable. kableExtra can customize either ",
+            "HTML or LaTeX outputs. See https://haozhu233.github.io/kableExtra/ ",
+            "for details.")
+    return(kable_input)
+  }
+  if (kable_format == "html") {
+    return(header_separate_html(kable_input, sep))
+  }
+  if (kable_format == "latex") {
+    return(header_separate_latex(kable_input, sep))
+  }
+}
+
+header_separate_html <- function(kable_input, sep) {
+  kable_attrs <- attributes(kable_input)
+  kable_xml <- kable_as_xml(kable_input)
+
+  kable_thead <- xml_tpart(kable_xml, "thead")
+  thead_depth <- length(xml_children(kable_thead))
+
+  if (thead_depth > 1) {
+    warning("Your table already has more than 1 rows of thead. header_separate ",
+            "won't work in this case and is returning the original input. ")
+    return(kable_input)
+  }
+
+  original_header_row <- xml_child(kable_thead, thead_depth)
+  original_header_cells <- lapply(
+    xml_children(original_header_row),
+    function(x) trimws(as.character(xml2::xml_contents(x)))
+  )
+
+  header_sep <- stringr::str_split(original_header_cells, sep)
+  header_layers <- process_header_sep(header_sep)
+  new_header_row_one <- lapply(header_layers[[1]], function(x) {
+    paste0("<th>", x, "</th>")
+  })
+
+  # Fix the original header row
+  for (i in seq(length(header_sep))) {
+    new_header_row_one[[i]] <- xml2::read_html(new_header_row_one[[i]])
+    xml2::xml_attrs(new_header_row_one[[i]]) <-
+      xml2::xml_attrs(xml_child(original_header_row, i))
+    xml2::xml_replace(xml_child(original_header_row, i),
+                      new_header_row_one[[i]])
+  }
+
+  out <- as_kable_xml(kable_xml)
+  attributes(out) <- kable_attrs
+  if (!"kableExtra" %in% class(out)) class(out) <- c("kableExtra", class(out))
+
+  for (l in seq(2, length(header_layers))) {
+    out <- kableExtra::add_header_above(
+      out, kableExtra::auto_index(header_layers[[l]])
+      )
+  }
+  return(out)
+}
+
+process_header_sep <- function(header_sep) {
+  max_depth <- max(unlist(lapply(header_sep, length)))
+  header_layers <- list()
+  for (i in seq(max_depth)) {
+    header_layers[[i]] <- list()
+    for (j in seq(1, length(header_sep))) {
+      layer_length <- length(header_sep[[j]])
+      if (layer_length > 0) {
+        header_layers[[i]][[j]] <- header_sep[[j]][layer_length]
+        header_sep[[j]] <- header_sep[[j]][-layer_length]
+      } else {
+        header_layers[[i]][[j]] <- " "
+      }
+    }
+  }
+  header_layers <- lapply(header_layers, unlist)
+  return(header_layers)
+}
+
+header_separate_latex <- function(kable_input, sep) {
+  table_info <- magic_mirror(kable_input)
+  out <- solve_enc(kable_input)
+
+  if (table_info$duplicated_rows) {
+    dup_fx_out <- fix_duplicated_rows_latex(out, table_info)
+    out <- dup_fx_out[[1]]
+    table_info <- dup_fx_out[[2]]
+  }
+
+  if (!is.null(table_info$new_header_row)) {
+    warning("Your table already has more than 1 rows of thead. header_separate ",
+            "won't work in this case and is returning the original input. ")
+    return(kable_input)
+  }
+
+  original_header_cells <- str_split(table_info$contents[1], " & ")[[1]]
+
+  header_sep <- stringr::str_split(original_header_cells, sep)
+  header_layers <- process_header_sep(header_sep)
+
+  # Fix the original header row
+  new_header_row_one <- paste0(header_layers[[1]], collapse = ' & ')
+
+  out <- stringr::str_replace(out, paste0(table_info$contents[1], "\\\\\\\\"),
+                              paste0(new_header_row_one, "\\\\\\\\"))
+  table_info$contents[1] <- new_header_row_one
+
+  out <- structure(out, format = "latex", class = "knitr_kable")
+  attr(out, "kable_meta") <- table_info
+
+  for (l in seq(2, length(header_layers))) {
+    out <- kableExtra::add_header_above(
+      out, kableExtra::auto_index(header_layers[[l]])
+    )
+  }
+
+  return(out)
+}
+
+