diff --git a/photonics.typ b/photonics.typ
index aff1007..7dc8f5a 100644
--- a/photonics.typ
+++ b/photonics.typ
@@ -168,6 +168,70 @@ $x in A arrow.l.r.double.long A in.rev x$
 ],[Alle Elemente der Grundmenge G welche nicht in A sind.],
 )
 
+=== Kartesisches Produkt
+
+== Funktionen
+Definition
+
+=== Urbild & Bild
+
+=== Identität
+
+=== Surjektivität, Injektivität, Bijektivität
+
+#cetz.canvas({
+  import cetz.draw: *
+  rect((0, 0), (1, 4))
+  content((0.5, 0.5), [1])
+  content((0.5, 1.5), [2])
+  content((0.5, 2.5), [3])
+  content((0.5, 3.5), [4])
+  rect((3, 0), (4, 3))
+  content((3.5, 0.5), [a])
+  content((3.5, 1.5), [b])
+  content((3.5, 2.5), [c])
+  line((1, 0.5), (3, 0.5), mark: (end: ">"), fill: black)
+  line((1, 1.5), (3, 1.5), mark: (end: ">"), fill: black)
+  line((1, 2.5), (3, 2.5), mark: (end: ">"), fill: black)
+  line((1, 3.5), (3, 2.5), mark: (end: ">"), fill: black)
+})
+
+#cetz.canvas({
+  import cetz.draw: *
+  rect((0, 0), (1, 3))
+  content((0.5, 0.5), [1])
+  content((0.5, 1.5), [2])
+  content((0.5, 2.5), [3])
+  rect((3, 0), (4, 4))
+  content((3.5, 0.5), [a])
+  content((3.5, 1.5), [b])
+  content((3.5, 2.5), [c])
+  content((3.5, 3.5), [d])
+  line((1, 0.5), (3, 0.5), mark: (end: ">"), fill: black)
+  line((1, 1.5), (3, 1.5), mark: (end: ">"), fill: black)
+  line((1, 2.5), (3, 2.5), mark: (end: ">"), fill: black)
+})
+
+#cetz.canvas({
+  import cetz.draw: *
+  rect((0, 0), (1, 4))
+  content((0.5, 0.5), [1])
+  content((0.5, 1.5), [2])
+  content((0.5, 2.5), [3])
+  content((0.5, 3.5), [4])
+  rect((3, 0), (4, 4))
+  content((3.5, 0.5), [a])
+  content((3.5, 1.5), [b])
+  content((3.5, 2.5), [c])
+  content((3.5, 3.5), [d])
+  line((1, 0.5), (3, 0.5), mark: (end: ">"), fill: black)
+  line((1, 1.5), (3, 1.5), mark: (end: ">"), fill: black)
+  line((1, 2.5), (3, 2.5), mark: (end: ">"), fill: black)
+  line((1, 3.5), (3, 3.5), mark: (end: ">"), fill: black)
+})
+
+== Folgen, Reihen & Grenzwerte
+
 
 #pagebreak()
 // }}}