diff --git a/biome.lisp b/biome.lisp
new file mode 100644
index 0000000..ac533c3
--- /dev/null
+++ b/biome.lisp
@@ -0,0 +1,57 @@
+;;;;
+;;;; Terra Nostra is a Minecraft-like survival game for the commandline.
+;;;;
+;;;; Biomes are habitat types, that provide default functions for patches.
+;;;; This file defines the biome struct and the inbuilt biomes.
+;;;; 
+;;;; (c) 2018 Daniel Vedder, MIT license
+;;;;
+
+;; Biome struct and register
+
+(defstruct biome
+	(name "")
+	(char #\.) ;map display character
+    (init-items '()) ;initial items for patches with this biome
+	(update-fn #'(lambda (patch-pos) NIL))) ;needs a patch position argument
+
+
+(let ((biome-list NIL))
+	(defun register-biome (symbol-name biome-object)
+		(setf biome-list (cons (list symbol-name biome-object) biome-list)))
+
+	(defun get-biome (symbol-name)
+		(cassoc symbol-name biome-list)))
+
+;; Grasslands biome
+
+(defun update-grasslands (patch-pos)
+	;;TODO
+	)
+
+(register-biome 'grassland
+	(make-biome :name "grassland" :char #\i
+		:init-items NIL ;TODO
+		:update-fn #'update-grasslands))
+
+;; Forest biome
+
+(defun update-forest (patch-pos)
+	;;TODO
+	)
+
+(register-biome 'forest
+	(make-biome :name "forest" :char #\Y
+		:init-items NIL ;TODO
+		:update-fn #'update-forest))
+
+;; Stream biome
+
+(defun update-stream (patch-pos)
+	;;TODO
+	)
+
+(register-biome 'stream
+	(make-biome :name "stream" :char #\~
+		:init-items NIL ;TODO
+		:update-fn #'update-stream))

diff --git a/biome.lisp b/biome.lisp
new file mode 100644
index 0000000..ac533c3
--- /dev/null
+++ b/biome.lisp
@@ -0,0 +1,57 @@
+;;;;
+;;;; Terra Nostra is a Minecraft-like survival game for the commandline.
+;;;;
+;;;; Biomes are habitat types, that provide default functions for patches.
+;;;; This file defines the biome struct and the inbuilt biomes.
+;;;; 
+;;;; (c) 2018 Daniel Vedder, MIT license
+;;;;
+
+;; Biome struct and register
+
+(defstruct biome
+	(name "")
+	(char #\.) ;map display character
+    (init-items '()) ;initial items for patches with this biome
+	(update-fn #'(lambda (patch-pos) NIL))) ;needs a patch position argument
+
+
+(let ((biome-list NIL))
+	(defun register-biome (symbol-name biome-object)
+		(setf biome-list (cons (list symbol-name biome-object) biome-list)))
+
+	(defun get-biome (symbol-name)
+		(cassoc symbol-name biome-list)))
+
+;; Grasslands biome
+
+(defun update-grasslands (patch-pos)
+	;;TODO
+	)
+
+(register-biome 'grassland
+	(make-biome :name "grassland" :char #\i
+		:init-items NIL ;TODO
+		:update-fn #'update-grasslands))
+
+;; Forest biome
+
+(defun update-forest (patch-pos)
+	;;TODO
+	)
+
+(register-biome 'forest
+	(make-biome :name "forest" :char #\Y
+		:init-items NIL ;TODO
+		:update-fn #'update-forest))
+
+;; Stream biome
+
+(defun update-stream (patch-pos)
+	;;TODO
+	)
+
+(register-biome 'stream
+	(make-biome :name "stream" :char #\~
+		:init-items NIL ;TODO
+		:update-fn #'update-stream))
diff --git a/terranostra.lisp b/terranostra.lisp
index ea7b4f9..1377574 100644
--- a/terranostra.lisp
+++ b/terranostra.lisp
@@ -2,17 +2,18 @@
 ;;;;
 ;;;; Terra Nostra is a Minecraft-like survival game for the commandline.
 ;;;; 
-;;;; (c) 2018 Daniel Vedder
+;;;; (c) 2018 Daniel Vedder, MIT license
 ;;;;
 
-;;(load "util.lisp") ;; I want to avoid using this if possible
+(load "util.lisp") ;; I want to avoid using this if possible
+(load "biome.lisp")
 
 (defvar *world* NIL)
 (defconstant *directions* '(N NE E SE S SW W NW))
 
 (defstruct patch
 	(pos '(0 0)) ;position
-	(char #\.))
+	(biome (make-biome)))
 
 
 (defun init-matrix (size)
@@ -81,12 +82,14 @@
 				((= x (length world)) (format tf "~&~A~%" xstr))
 				;;TODO
 				(setf xstr (concatenate 'string xstr (unless (= x 0) ",")
-							   (format NIL "~S" (patch-char (nth x row)))))))))
+							   (format NIL "~S"
+								   (biome-char (patch-biome (nth x row))))))))))
 
 
 (defun create-world (size name &optional (world *world*))
 	(setf world NIL)
 	(setf world (init-matrix size))
+	;;TODO
 	(save-topography name world))
 
 ;; Initialize the random state (which would otherwise not be very random...)