diff --git a/DESCRIPTION b/DESCRIPTION
index 7f6dd2b..6b618a5 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -36,7 +36,8 @@ Imports:
     methods,
     lifecycle,
     pbapply,
-    knitr
+    knitr,
+    scales
 Suggests:
     testthat (>= 3.0.0),
     vdiffr (>= 1.0.0),
diff --git a/NAMESPACE b/NAMESPACE
index 07334d5..fc16bcc 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -25,10 +25,13 @@ export(recolor_phylopic)
 export(resolve_phylopic)
 export(rotate_phylopic)
 export(save_phylopic)
+export(scale_height_continuous)
+export(scale_width_continuous)
 importFrom(curl,nslookup)
 importFrom(ggplot2,Geom)
 importFrom(ggplot2,aes)
 importFrom(ggplot2,annotate)
+importFrom(ggplot2,continuous_scale)
 importFrom(ggplot2,coord_equal)
 importFrom(ggplot2,element_text)
 importFrom(ggplot2,expansion)
@@ -40,6 +43,7 @@ importFrom(ggplot2,layer)
 importFrom(ggplot2,remove_missing)
 importFrom(ggplot2,theme)
 importFrom(ggplot2,theme_void)
+importFrom(ggplot2,waiver)
 importFrom(grDevices,bmp)
 importFrom(grDevices,col2rgb)
 importFrom(grDevices,dev.off)
@@ -81,6 +85,7 @@ importFrom(pbapply,pblapply)
 importFrom(png,readPNG)
 importFrom(rsvg,rsvg_png)
 importFrom(rsvg,rsvg_svg)
+importFrom(scales,pal_area)
 importFrom(stats,setNames)
 importFrom(utils,URLdecode)
 importFrom(utils,URLencode)
diff --git a/R/geom_phylopic.R b/R/geom_phylopic.R
index acaed08..1673738 100644
--- a/R/geom_phylopic.R
+++ b/R/geom_phylopic.R
@@ -499,6 +499,40 @@ phylopicGrob <- function(img, x, y, height, width,
   return(img_grob)
 }
 
+#' Scales for phylopic heighgt or width
+#'
+#' `scale_height_continuous()` scales the height of silhouettes whereas
+#' `scale_width_continuous()` scales the height of silhouettes. 
+#' @inheritParams ggplot2::scale_size_continuous
+#' @export
+#' @importFrom ggplot2 continuous_scale waiver
+#' @importFrom scales pal_area
+#' @rdname scales
+scale_height_continuous <- function(name = waiver(), breaks = waiver(), labels = waiver(),
+                                    limits = NULL, range = c(1, 6),
+                                    transform = "identity",
+                                    trans = lifecycle::deprecated(),
+                                    guide = "none") {
+  continuous_scale("height", palette = scales::pal_area(range), name = name,
+                   breaks = breaks, labels = labels, limits = limits,
+                   transform = transform, trans = trans, guide = guide)
+}
+
+#' @inheritParams ggplot2::scale_size_continuous
+#' @export
+#' @importFrom ggplot2 continuous_scale waiver
+#' @importFrom scales pal_area
+#' @rdname scales
+scale_width_continuous <- function(name = waiver(), breaks = waiver(), labels = waiver(),
+                                    limits = NULL, range = c(1, 6),
+                                    transform = "identity",
+                                    trans = lifecycle::deprecated(),
+                                    guide = "none") {
+  continuous_scale("width", palette = scales::pal_area(range), name = name,
+                   breaks = breaks, labels = labels, limits = limits,
+                   transform = transform, trans = trans, guide = guide)
+}
+
 #' @importFrom grid grobName
 ggname <- function(prefix, grob) {
   # copied from ggplot2
diff --git a/man/scales.Rd b/man/scales.Rd
new file mode 100644
index 0000000..18a8cc9
--- /dev/null
+++ b/man/scales.Rd
@@ -0,0 +1,98 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/geom_phylopic.R
+\name{scale_height_continuous}
+\alias{scale_height_continuous}
+\alias{scale_width_continuous}
+\title{Scales for phylopic heighgt or width}
+\usage{
+scale_height_continuous(
+  name = waiver(),
+  breaks = waiver(),
+  labels = waiver(),
+  limits = NULL,
+  range = c(1, 6),
+  transform = "identity",
+  trans = lifecycle::deprecated(),
+  guide = "none"
+)
+
+scale_width_continuous(
+  name = waiver(),
+  breaks = waiver(),
+  labels = waiver(),
+  limits = NULL,
+  range = c(1, 6),
+  transform = "identity",
+  trans = lifecycle::deprecated(),
+  guide = "none"
+)
+}
+\arguments{
+\item{name}{The name of the scale. Used as the axis or legend title. If
+\code{waiver()}, the default, the name of the scale is taken from the first
+mapping used for that aesthetic. If \code{NULL}, the legend title will be
+omitted.}
+
+\item{breaks}{One of:
+\itemize{
+\item \code{NULL} for no breaks
+\item \code{waiver()} for the default breaks computed by the
+\link[scales:new_transform]{transformation object}
+\item A numeric vector of positions
+\item A function that takes the limits as input and returns breaks
+as output (e.g., a function returned by \code{\link[scales:breaks_extended]{scales::extended_breaks()}}).
+Note that for position scales, limits are provided after scale expansion.
+Also accepts rlang \link[rlang:as_function]{lambda} function notation.
+}}
+
+\item{labels}{One of:
+\itemize{
+\item \code{NULL} for no labels
+\item \code{waiver()} for the default labels computed by the
+transformation object
+\item A character vector giving labels (must be same length as \code{breaks})
+\item An expression vector (must be the same length as breaks). See ?plotmath for details.
+\item A function that takes the breaks as input and returns labels
+as output. Also accepts rlang \link[rlang:as_function]{lambda} function
+notation.
+}}
+
+\item{limits}{One of:
+\itemize{
+\item \code{NULL} to use the default scale range
+\item A numeric vector of length two providing limits of the scale.
+Use \code{NA} to refer to the existing minimum or maximum
+\item A function that accepts the existing (automatic) limits and returns
+new limits. Also accepts rlang \link[rlang:as_function]{lambda} function
+notation.
+Note that setting limits on positional scales will \strong{remove} data outside of the limits.
+If the purpose is to zoom, use the limit argument in the coordinate system
+(see \code{\link[ggplot2:coord_cartesian]{coord_cartesian()}}).
+}}
+
+\item{range}{a numeric vector of length 2 that specifies the minimum and
+maximum size of the plotting symbol after transformation.}
+
+\item{transform}{For continuous scales, the name of a transformation object
+or the object itself. Built-in transformations include "asn", "atanh",
+"boxcox", "date", "exp", "hms", "identity", "log", "log10", "log1p", "log2",
+"logit", "modulus", "probability", "probit", "pseudo_log", "reciprocal",
+"reverse", "sqrt" and "time".
+
+A transformation object bundles together a transform, its inverse,
+and methods for generating breaks and labels. Transformation objects
+are defined in the scales package, and are called \verb{transform_<name>}. If
+transformations require arguments, you can call them from the scales
+package, e.g. \code{\link[scales:transform_boxcox]{scales::transform_boxcox(p = 2)}}.
+You can create your own transformation with \code{\link[scales:new_transform]{scales::new_transform()}}.}
+
+\item{trans}{\ifelse{html}{\href{https://lifecycle.r-lib.org/articles/stages.html#deprecated}{\figure{lifecycle-deprecated.svg}{options: alt='[Deprecated]'}}}{\strong{[Deprecated]}} Deprecated in favour of
+\code{transform}.}
+
+\item{guide}{A function used to create a guide or its name. See
+\code{\link[ggplot2:guides]{guides()}} for more information.}
+}
+\description{
+\code{scale_height_continuous()} scales the height of silhouettes whereas
+\code{scale_width_continuous()} scales the height of silhouettes.
+}