diff --git a/collects/teachpack/htdp/scribblings/htdp.scrbl b/collects/teachpack/htdp/scribblings/htdp.scrbl
index e59097b750..7f8f880942 100644
--- a/collects/teachpack/htdp/scribblings/htdp.scrbl
+++ b/collects/teachpack/htdp/scribblings/htdp.scrbl
@@ -24,6 +24,8 @@
 @include-section["elevator.scrbl"]
 @include-section["show-queen.scrbl"]
 
+@include-section["matrix.scrbl"]
+
 @;-- what do those do? --
 
 @;include-section["guess-gui.scrbl"]
diff --git a/collects/teachpack/htdp/scribblings/matrix.scrbl b/collects/teachpack/htdp/scribblings/matrix.scrbl
new file mode 100644
index 0000000000..9114db92f3
--- /dev/null
+++ b/collects/teachpack/htdp/scribblings/matrix.scrbl
@@ -0,0 +1,72 @@
+#lang scribble/doc
+
+@(require scribble/manual "shared.ss"
+          (for-label scheme
+                     teachpack/htdp/image
+                     teachpack/htdp/world
+                     lang/private/imageeq))
+
+@teachpack["matrix"]{Matrix Operations}
+
+The teachpack supports matrices and matrix operations. A matrix is just a
+rectangle of 'objects'. It is displayed as an image, just like the images
+from @secref["image"]. 
+
+@declare-exporting[teachpack/htdp/matrix]
+
+@deftech{Rectangle} 
+A Rectangle (of X) is a non-empty list of lists containing X where all
+elements of the list are lists of equal (non-zero) length.
+
+@defproc[(matrix? [o any/c]) boolean?]{
+determines whether the given object is a matrix?}
+
+@defproc[(matrix-rows [m matrix?]) natural-number/c]{
+determines how many rows this matrix @scheme[m] has} 
+
+@defproc[(matrix-cols [m matrix?]) natural-number/c]{
+determines ow many columns this matrix @scheme[m] has} 
+
+@defproc[(rectangle->matrix [r (unsyntax @tech{Rectangle})]) matrix?]{
+creates a matrix from the given @tech{Rectangle}}
+
+@defproc[(matrix->rectangle [m matrix?]) (unsyntax @tech{Rectangle})]{
+creates a rectangle from this matrix @scheme[m]}
+
+@defproc[(make-matrix [n natural-number/c][m natural-number/c][l (Listof X)]) matrix?]{
+creates an @scheme[n] by @scheme[m] matrix from @scheme[l] 
+
+NOTE: make-matrix would consume an optional number of entries, if it were
+like make-vector}
+
+@defproc[(build-matrix [n natural-number/c][m natural-number/c]
+                       [f (-> natural-number/c natural-number/c any)])
+         matrix?]{
+creates an @scheme[n] by @scheme[m] matrix by applying @scheme[f] to (0,0),
+(0,1), ..., (n-1,m-1)}
+
+@defproc[(matrix-ref [m matrix?][i natural-number/c][j natural-number/c]) any]{
+retrieve the item at (@scheme[i],@scheme[j]) in matrix @scheme[m]}
+
+@defproc[(matrix-set [m matrix?][i natural-number/c][j natural-number/c] 
+		     [x any/c]) 
+         matrix?]{
+creates a new matrix with @scheme[x] at (@scheme[i],@scheme[j]) and all
+other places the same as in @scheme[m]}
+
+@defproc[(matrix-where? [m matrix?] [pred? (-> any/c boolean?)]) (listof posn?)]{
+@scheme[(matrix-where? M P)] produces a list of @scheme[(make-posn i j)]
+such that @scheme[(P (matrix-ref M i j))] holds}
+
+@defproc[(matrix-render [m matrix?]) (unsyntax @tech{Rectangle})]{
+renders this matrix @scheme[m] as a rectangle of strings}
+
+@defproc[(matrix-minor [m matrix?][i natural-number/c][j natural-number/c]) 
+          matrix?]{ 
+creates a matrix minor from @scheme[m] at (@scheme[i],@scheme[j])}
+
+@defproc[(matrix-set! [m matrix?][i natural-number/c][j natural-number/c]
+		      [x any/c])
+         matrix?]{
+like @scheme[matrix-set] but uses a destructive update}
+