diff --git a/src/App/App.cpp b/src/App/App.cpp
index dff250b..6600c13 100644
--- a/src/App/App.cpp
+++ b/src/App/App.cpp
@@ -10,6 +10,7 @@ namespace Dough
 
     App::App() : config(),
                  ui(onoffButtonInterruptCallback, setupButtonInterruptCallback),
+                 state(&ui),
                  wifi(),
                  mqtt(&wifi, mqttOnConnectCallback, mqttOnMessageCallback),
                  sensorControllerPlugin(&mqtt, &ui),
@@ -34,17 +35,89 @@ namespace Dough
         distanceSensor.setup();
     }
 
-    void App::measure()
+    void App::loop()
     {
-        if (!config.isOk())
+        if (_setupNetworkConnection())
         {
-            return;
+            ui.processButtonEvents();
+            mqtt.procesIncomingsMessages();
+
+            switch (state.get())
+            {
+            case CONFIGURING:
+                if (config.isOk())
+                {
+                    state.startMeasurements();
+                }
+                break;
+            case MEASURING:
+                if (config.isOk())
+                {
+                    temperatureSensor.loop();
+                    humiditySensor.loop();
+                    distanceSensor.loop();
+                }
+                else
+                {
+                    state.startConfiguration();
+                }
+                break;
+            }
+        }
+    }
+
+    // Check if the device is connected to the WiFi network and the MQTT broker.
+    // If not, then try to setup the connection.
+    // Returns true if the connection was established, false otherwise.
+    bool App::_setupNetworkConnection()
+    {
+        static bool connected = false;
+
+        if (!wifi.isConnected())
+        {
+            state.setWiFiConnected(false);
+            if (connected)
+            {
+                _logger.log("s", "ERROR - Connection to WiFi network lost! Reconnecting ...");
+            }
+            else
+            {
+                _logger.log("s", "Connecting to the WiFi network ...");
+            }
+            connected = false;
+            ui.notifyConnectingToWifi();
+            state.setWiFiConnected(wifi.connect());
+        }
+        if (wifi.isConnected() && !mqtt.isConnected())
+        {
+            state.setWiFiConnected(true);
+            state.setMQTTConnected(false);
+            if (connected)
+            {
+                _logger.log("s", "ERROR - Connection to the MQTT broker lost! Reconnecting ...");
+            }
+            else
+            {
+                _logger.log("s", "Connecting to the MQTT broker ...");
+            }
+            connected = false;
+            ui.notifyConnectingToMQTT();
+            state.setMQTTConnected(mqtt.connect());
+        }
+        if (wifi.isConnected() && mqtt.isConnected())
+        {
+            state.setWiFiConnected(true);
+            state.setMQTTConnected(true);
+            if (!connected)
+            {
+                _logger.log("s", "Connection to MQTT broker established");
+                ui.notifyConnected();
+                ui.clearButtonEvents();
+                connected = true;
+            }
         }
 
-        // Get measurements from the sensors.
-        temperatureSensor.loop();
-        humiditySensor.loop();
-        distanceSensor.loop();
+        return connected;
     }
 
     void App::clearHistory()
diff --git a/src/App/App.h b/src/App/App.h
index c289182..78e32b6 100644
--- a/src/App/App.h
+++ b/src/App/App.h
@@ -2,6 +2,7 @@
 #define DOUGH_APP_H
 
 #include <Arduino.h>
+#include "App/AppStateController.h"
 #include "UI/UI.h"
 #include "App/Configuration.h"
 #include "App/callbacks.h"
@@ -20,6 +21,7 @@ namespace Dough
         static App *Instance();
         Configuration config;
         UI ui;
+        AppStateController state;
         WiFi wifi;
         MQTT mqtt;
         SensorControllerPlugin sensorControllerPlugin;
@@ -28,12 +30,13 @@ namespace Dough
         SensorController humiditySensor;
 
         void setup();
-        void measure();
+        void loop();
         void clearHistory();
                 
     private:
         App();
         Logger _logger;
+        bool _setupNetworkConnection();
     };
 }
 
diff --git a/src/App/AppStateController.cpp b/src/App/AppStateController.cpp
new file mode 100644
index 0000000..d6ad2ad
--- /dev/null
+++ b/src/App/AppStateController.cpp
@@ -0,0 +1,102 @@
+#include "App/AppStateController.h"
+
+namespace Dough
+{
+    AppStateController::AppStateController(AppStateControllerPluginBase *plugin) : _logger("STATE"),
+                                                                                   _plugin(plugin) {}
+
+    AppState AppStateController::get()
+    {
+        if (_wifiConnected != CONNECTED)
+        {
+            return _wifiConnected == CONNECTION_LOST ? WIFI_CONNECTION_LOST : CONNECTING_WIFI;
+        }
+        if (_mqttConnected != CONNECTED)
+        {
+            return _mqttConnected == CONNECTION_LOST ? MQTT_CONNECTION_LOST : CONNECTING_MQTT;
+        }
+        if (_operationMode == CONFIGURE)
+        {
+            return CONFIGURING;
+        }
+        if (_operationMode == MEASURE)
+        {
+            return _paused ? PAUSED : MEASURING;
+            ;
+        }
+        if (_operationMode == CALIBRATE)
+        {
+            return CALIBRATING;
+        }
+        _logger.log("s", "get(): Unable to determine state!");
+        return INVALID;
+    }
+
+    void AppStateController::setWiFiConnected(bool connected)
+    {
+        if (connected)
+        {
+            _wifiConnected = CONNECTED;
+        }
+        else
+        {
+            _wifiConnected = _wifiConnected == CONNECTED ? CONNECTION_LOST : CONNECTING;
+            setMQTTConnected(false);
+        }
+        _updateState();
+    }
+
+    void AppStateController::setMQTTConnected(bool connected)
+    {
+        if (connected)
+        {
+            _mqttConnected = CONNECTED;
+        }
+        else
+        {
+            _mqttConnected = _mqttConnected == CONNECTED ? CONNECTION_LOST : CONNECTING;
+        }
+        _updateState();
+    }
+
+    void AppStateController::startConfiguration()
+    {
+        _operationMode = CONFIGURE;
+        _updateState();
+    }
+
+    void AppStateController::startMeasurements()
+    {
+        _operationMode = MEASURE;
+        _updateState();
+    }
+
+    void AppStateController::startCalibration()
+    {
+        _operationMode = CALIBRATE;
+        _updateState();
+    }
+
+    void AppStateController::pauseMeasurements()
+    {
+        _paused = true;
+        _updateState();
+    }
+
+    void AppStateController::resumeMeasurements()
+    {
+        _paused = false;
+        _updateState();
+    }
+
+    void AppStateController::_updateState()
+    {
+        auto oldState = _appState;
+        auto newState = get();
+        if (newState != oldState)
+        {
+            _plugin->onStateChange(oldState, newState);
+            _appState = newState;
+        }
+    }
+} // namespace Dough
diff --git a/src/App/AppStateController.h b/src/App/AppStateController.h
new file mode 100644
index 0000000..26cd681
--- /dev/null
+++ b/src/App/AppStateController.h
@@ -0,0 +1,70 @@
+#ifndef DOUGH_STATEMACHINE_H
+#define DOUGH_STATEMACHINE_H
+
+#include <Arduino.h>
+#include "UI/Logger.h"
+
+namespace Dough
+{
+    typedef enum
+    {
+        INITIALIZING,
+        WIFI_CONNECTION_LOST,
+        CONNECTING_WIFI,
+        MQTT_CONNECTION_LOST,
+        CONNECTING_MQTT,
+        CONFIGURING,
+        MEASURING,
+        CALIBRATING,
+        PAUSED,
+        INVALID
+    } AppState;
+
+    typedef enum
+    {
+        CONNECTING,
+        CONNECTED,
+        CONNECTION_LOST
+    } ConnectionState;
+
+    typedef enum
+    {
+        CONFIGURE,
+        MEASURE,
+        CALIBRATE
+    } AppOperationMode;
+
+    // This class defines an interface that can be implemented to create a plugin
+    // for the Dough::AppState class. This plugin can act upon state changes.
+    class AppStateControllerPluginBase
+    {
+    public:
+        virtual void onStateChange(AppState oldState, AppState newState);
+    };
+
+    class AppStateController
+    {
+    public:
+        AppStateController(AppStateControllerPluginBase *plugin);
+        void setWiFiConnected(bool connected);
+        void setMQTTConnected(bool connected);
+        void startConfiguration();
+        void startMeasurements();
+        void startCalibration();
+        void pauseMeasurements();
+        void resumeMeasurements();
+        AppState get();
+
+    private:
+        Logger _logger;
+        AppStateControllerPluginBase *_plugin;
+        AppState _appState = INITIALIZING;
+        ConnectionState _wifiConnected = CONNECTING;
+        ConnectionState _mqttConnected = CONNECTING;
+        AppOperationMode _operationMode = CONFIGURE;
+        bool _paused = false;
+        void _updateState();
+    };
+} // namespace Dough
+
+#endif
\ No newline at end of file
diff --git a/src/Sensors/SensorController.h b/src/Sensors/SensorController.h
index f9d1cbd..4218536 100644
--- a/src/Sensors/SensorController.h
+++ b/src/Sensors/SensorController.h
@@ -11,7 +11,7 @@ namespace Dough
     // This class is used to store measurements for a sensor and to keep
     // track of running totals for handling average computations.
     // It also provides functionality to decide when to read a measurement
-    // from a sensor and when to publish measurements  (after significant
+    // from a sensor and when to publish measurements (after significant
     // changes occur or when the last publish was too long ago).
     class SensorController;
 
diff --git a/src/UI/UI.cpp b/src/UI/UI.cpp
index 5162e30..90bd1e5 100644
--- a/src/UI/UI.cpp
+++ b/src/UI/UI.cpp
@@ -112,6 +112,13 @@ namespace Dough
         _led3.loop();
     }
 
+    void UI::onStateChange(AppState oldState, AppState newState)
+    {
+        Serial.print(oldState); // TODO
+        Serial.print(" to ");
+        Serial.println(newState); // TODO
+    }
+
     void UI::notifyConnectingToWifi()
     {
         _led1.blink()->slow();
diff --git a/src/UI/UI.h b/src/UI/UI.h
index a90dd3e..1e38616 100644
--- a/src/UI/UI.h
+++ b/src/UI/UI.h
@@ -3,6 +3,7 @@
 
 #include <Arduino.h>
 #include <stdarg.h>
+#include "App/AppStateController.h"
 #include "UI/Button.h"
 #include "UI/LED.h"
 #include "config.h"
@@ -11,7 +12,7 @@ namespace Dough
 {
     // This class groups all user interface functionality: serial logging,
     // LEDs and buttons.
-    class UI
+    class UI : public AppStateControllerPluginBase
     {
     public:
         UI(ButtonISR onoffButtonISR, ButtonISR setupButtonISR);
@@ -23,6 +24,7 @@ namespace Dough
         void updateLEDs();
         void resume();
         void suspend();
+        virtual void onStateChange(AppState oldState, AppState newState);
         void notifyConnectingToWifi();
         void notifyConnectingToMQTT();
         void notifyConnected();
diff --git a/src/main.cpp b/src/main.cpp
index bf689f6..1a31126 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1,9 +1,5 @@
 #include "main.h"
 
-// TOOD: implement the calibration logic
-// TODO: don't make sensors instances anymore, now they are handled by App as the only singleton
-// TODO: see what more stuff can be moved to the UI code. Maybe state to UI state translation ought to be there as well
-
 DoughBoyState state = CONFIGURING;
 Dough::Logger logger("MAIN");
 
@@ -21,93 +17,32 @@ void setup()
 void loop()
 {
     auto app = Dough::App::Instance();
-
-    app->ui.processButtonEvents();
-
-    if (!setupNetworkConnection())
-    {
-        return;
-    }
+    app->loop();
     
-    app->mqtt.procesIncomingsMessages();
-    
-    if (state == CONFIGURING)
-    {
-        if (app->config.isOk())
-        {
-            setStateToMeasuring();
-        }
-    }
-    else if (state == MEASURING && !app->config.isOk())
-    {
-        setStateToConfiguring();
-    }
-    else if (state == MEASURING)
-    {
-        app->measure();
-    }
-    else if (state == CALIBRATING)
-    {
-        delay(3000);
-        setStateToPaused();
-    }
-    else if (state == PAUSED)
-    {
-        app->clearHistory();
-    }
-}
-
-// Check if the device is connected to the WiFi network and the MQTT broker.
-// If not, then try to setup the connection.
-// Returns true if the connection was established, false otherwise.
-bool setupNetworkConnection()
-{
-    static auto connectionState = CONNECTING_WIFI;
-
-    auto app = Dough::App::Instance();
-
-    if (!app->wifi.isConnected())
-    {
-        if (connectionState == CONNECTED)
-        {
-            logger.log("s", "ERROR - Connection to WiFi network lost! Reconnecting ...");
-        }
-        else
-        {
-            logger.log("s", "Connecting to the WiFi network ...");
-        }
-        connectionState = CONNECTING_WIFI;
-        app->ui.notifyConnectingToWifi();
-        app->wifi.connect();
-    }
-    if (app->wifi.isConnected() && !app->mqtt.isConnected())
-    {
-        if (connectionState == CONNECTED)
-        {
-            logger.log("s", "ERROR - Connection to the MQTT broker lost! Reconnecting ...");
-        }
-        else
-        {
-            logger.log("s", "Connecting to the MQTT broker ...");
-        }
-        connectionState = CONNECTING_MQTT;
-        app->ui.notifyConnectingToMQTT();
-        app->mqtt.connect();
-        delay(1000); // purely costmetic, to make the faster LED blinking noticable
-    }
-    if (app->wifi.isConnected() && app->mqtt.isConnected())
-    {
-        if (connectionState != CONNECTED)
-        {
-            logger.log("s", "Connection to MQTT broker established");
-            app->ui.notifyConnected();
-            app->ui.clearButtonEvents();
-            connectionState = CONNECTED;
-            setStateToConfiguring();
-        }
-    }
-
-    return connectionState == CONNECTED;
+    // if (state == CONFIGURING)
+    // {
+    //     if (app->config.isOk())
+    //     {
+    //         setStateToMeasuring();
+    //     }
+    // }
+    // else if (state == MEASURING && !app->config.isOk())
+    // {
+    //     setStateToConfiguring();
+    // }
+    // else if (state == MEASURING)
+    // {
+    //     app->measure();
+    // }
+    // else if (state == CALIBRATING)
+    // {
+    //     delay(3000);
+    //     setStateToPaused();
+    // }
+    // else if (state == PAUSED)
+    // {
+    //     app->clearHistory();
+    // }
 }
 
 void handleOnoffButtonPress()
diff --git a/src/main.h b/src/main.h
index 81eb77a..3a5b3b0 100644
--- a/src/main.h
+++ b/src/main.h
@@ -12,13 +12,6 @@
 #include "UI/UI.h"
 #include "config.h"
 
-typedef enum
-{
-    CONNECTING_WIFI,
-    CONNECTING_MQTT,
-    CONNECTED
-} DoughBoyConnectionState;
-
 typedef enum
 {
     CONFIGURING,
@@ -27,10 +20,9 @@ typedef enum
     CALIBRATING
 } DoughBoyState;
 
-bool setupNetworkConnection();
-void handleMqttMessage(String &topic, String &payload);
 void handleOnoffButtonPress();
 void handleSetupButtonPress();
+
 void setStateToConfiguring();
 void setStateToMeasuring();
 void setStateToPaused();