diff --git a/maidroid/api.lua b/maidroid/api.lua
index 8ad79d2..4d218e5 100644
--- a/maidroid/api.lua
+++ b/maidroid/api.lua
@@ -57,6 +57,17 @@ function maidroid.get_core(self)
 	return nil
 end
 
+-- maidroid.register_core registers a definition of a new core.
+function maidroid.register_core(core_name, def)
+	maidroid.registered_cores[core_name] = def
+
+	minetest.register_craftitem(core_name, {
+		stack_max       = 1,
+		description     = def.description,
+		inventory_image = def.inventory_image,
+	})
+end
+
 -- maidroid.register_maidroid registers a definition of a new maidroid.
 function maidroid.register_maidroid(product_name, def)
 
@@ -69,7 +80,6 @@ function maidroid.register_maidroid(product_name, def)
 				if listname == "core" then
 					local core_name = stack:get_name()
 					local core = registered_cores[core_name]
-
 					core.initialize(self)
 					self.core_name = core_name
 				end
@@ -88,7 +98,6 @@ function maidroid.register_maidroid(product_name, def)
 			on_take = function(inv, listname, index, stack, player)
 				if listname == "core" then
 					local core = registered_cores[self.core_name]
-
 					self.core_name = ""
 					core.finalize(self)
 				end
diff --git a/maidroid/init.lua b/maidroid/init.lua
index 65b2e54..7cd0eb1 100644
--- a/maidroid/init.lua
+++ b/maidroid/init.lua
@@ -9,3 +9,4 @@ maidroid.modname = "maidroid"
 maidroid.modpath = maidroid.get_modpath(maidroid.modname)
 
 dofile(maidroid.modpath .. "/api.lua")
+dofile(maidroid.modpath .. "/register.lua")
diff --git a/maidroid/models/maidroid.png b/maidroid/models/maidroid_mk1.png
similarity index 100%
rename from maidroid/models/maidroid.png
rename to maidroid/models/maidroid_mk1.png
diff --git a/maidroid/models/maidroid_mk2.png b/maidroid/models/maidroid_mk2.png
new file mode 100644
index 0000000..97690e1
Binary files /dev/null and b/maidroid/models/maidroid_mk2.png differ
diff --git a/maidroid/models/maidroid_mk3.png b/maidroid/models/maidroid_mk3.png
new file mode 100644
index 0000000..5436d06
Binary files /dev/null and b/maidroid/models/maidroid_mk3.png differ
diff --git a/maidroid/register.lua b/maidroid/register.lua
new file mode 100644
index 0000000..236cbda
--- /dev/null
+++ b/maidroid/register.lua
@@ -0,0 +1,25 @@
+------------------------------------------------------------
+-- Copyright (c) 2016 tacigar
+-- https://github.com/tacigar/maidroid
+------------------------------------------------------------
+
+maidroid.register_maidroid("maidroid:maidroid_mk1", {
+	hp_max    = 10,
+	weight    = 20,
+	mesh      = "maidroid.b3d",
+	textures  = "maidroid_mk1.png",
+})
+
+maidroid.register_maidroid("maidroid:maidroid_mk2", {
+	hp_max    = 10,
+	weight    = 20,
+	mesh      = "maidroid.b3d",
+	textures  = "maidroid_mk2.png",
+})
+
+maidroid.register_maidroid("maidroid:maidroid_mk3", {
+	hp_max    = 10,
+	weight    = 20,
+	mesh      = "maidroid.b3d",
+	textures  = "maidroid_mk3.png",
+})