diff --git a/PettingZoo.Test/Tapeti/TypeToJObjectTest.cs b/PettingZoo.Test/Tapeti/TypeToJObjectTest.cs
index a02dcb0..de554a0 100644
--- a/PettingZoo.Test/Tapeti/TypeToJObjectTest.cs
+++ b/PettingZoo.Test/Tapeti/TypeToJObjectTest.cs
@@ -34,7 +34,7 @@ namespace PettingZoo.Test.Tapeti
                 objectValue.Should().HaveElement("RecursiveValue").Which.Type.Should().Be(JTokenType.Null);
 
                 // Via type mapping
-                // TODO
+                // TODO test type mappings
             }
         }
 
diff --git a/PettingZoo/UI/Tab/Subscriber/SameMessageVisibilityConverter.cs b/PettingZoo/UI/Tab/Subscriber/SameMessageVisibilityConverter.cs
new file mode 100644
index 0000000..4f6df58
--- /dev/null
+++ b/PettingZoo/UI/Tab/Subscriber/SameMessageVisibilityConverter.cs
@@ -0,0 +1,23 @@
+using System;
+using System.Globalization;
+using System.Windows;
+using System.Windows.Data;
+
+namespace PettingZoo.UI.Tab.Subscriber
+{
+    public class SameMessageVisibilityConverter : IMultiValueConverter
+    {
+        public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
+        {
+            return ReferenceEquals(values[0], values[1])
+                ? Visibility.Visible
+                : Visibility.Collapsed;
+        }
+
+
+        public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
+        {
+            throw new NotSupportedException();
+        }
+    }
+}
diff --git a/PettingZoo/UI/Tab/Subscriber/SubscriberView.xaml b/PettingZoo/UI/Tab/Subscriber/SubscriberView.xaml
index 95a1f1b..5684e93 100644
--- a/PettingZoo/UI/Tab/Subscriber/SubscriberView.xaml
+++ b/PettingZoo/UI/Tab/Subscriber/SubscriberView.xaml
@@ -11,6 +11,9 @@
              d:DesignWidth="800"
              d:DataContext="{d:DesignInstance res:DesignTimeSubscriberViewModel, IsDesignTimeCreatable=True}"
              Background="White">
+    <UserControl.Resources>
+        <res:SameMessageVisibilityConverter x:Key="SameMessageVisibilityConverter" />
+    </UserControl.Resources>
     <Grid Margin="4">
         <Grid.ColumnDefinitions>
             <ColumnDefinition Width="*" />
@@ -30,11 +33,37 @@
                 <DataTemplate>
                     <Grid>
                         <Grid.ColumnDefinitions>
-                            <ColumnDefinition Width="Auto" MinWidth="150"/>
-                            <ColumnDefinition Width="*"/>
+                            <ColumnDefinition Width="Auto" MinWidth="150" SharedSizeGroup="DateTime"/>
+                            <ColumnDefinition Width="*" />
                         </Grid.ColumnDefinitions>
-                        <TextBlock Grid.Column="0" Grid.Row="0" Text="{Binding ReceivedTimestamp, StringFormat=g}" Style="{StaticResource Timestamp}"></TextBlock>
-                        <TextBlock Grid.Column="1" Grid.Row="0" Text="{Binding RoutingKey}" Style="{StaticResource RoutingKey}"></TextBlock>
+
+                        <Grid.RowDefinitions>
+                            <RowDefinition Height="Auto" />
+                            <RowDefinition Height="Auto" />
+                        </Grid.RowDefinitions>
+
+                        <!-- TODO insert as non-focusable item instead, so it's not part of the selection (and perhaps also fixes the bug mentioned in SubscriberViewModel) -->
+                        <Grid Grid.Column="0" Grid.Row="0" Grid.ColumnSpan="2">
+                            <Grid.ColumnDefinitions>
+                                <ColumnDefinition SharedSizeGroup="DateTime" />
+                                <ColumnDefinition Width="Auto" />
+                                <ColumnDefinition Width="*" />
+                            </Grid.ColumnDefinitions>
+
+                            <Grid.Visibility>
+                                <MultiBinding Converter="{StaticResource SameMessageVisibilityConverter}">
+                                    <Binding RelativeSource="{RelativeSource Self}" Path="DataContext" />
+                                    <Binding RelativeSource="{RelativeSource AncestorType={x:Type ListBox}}" Path="DataContext.NewMessage" />
+                                </MultiBinding>
+                            </Grid.Visibility>
+
+                            <Separator Grid.Column="0" Margin="0,0,8,0" />
+                            <TextBlock Grid.Column="1" Text="{x:Static res:SubscriberViewStrings.LabelNewMessages}" HorizontalAlignment="Center" Background="{Binding Background, RelativeSource={RelativeSource AncestorType={x:Type ListBoxItem}}}" Foreground="{x:Static SystemColors.GrayTextBrush}" />
+                            <Separator Grid.Column="2" Margin="8,0,0,0" />
+                        </Grid>
+
+                        <TextBlock Grid.Column="0" Grid.Row="1" Text="{Binding ReceivedTimestamp, StringFormat=g}" Style="{StaticResource Timestamp}" />
+                        <TextBlock Grid.Column="1" Grid.Row="1" Text="{Binding RoutingKey}" Style="{StaticResource RoutingKey}" />
 
                         <Grid.ContextMenu>
                             <ContextMenu>
@@ -66,6 +95,8 @@
             <Border Grid.Column="0" Grid.Row="1" Style="{StaticResource SidePanel}">
                 <DockPanel>
                     <Label DockPanel.Dock="Top" Style="{StaticResource HeaderLabel}" Content="{x:Static res:SubscriberViewStrings.PanelTitleBody}"/>
+
+                    <!-- TODO use AvalonEdit with syntax highlighting depending on content type -->
                     <TextBox 
                             Text="{Binding SelectedMessageBody, Mode=OneWay}" 
                             BorderThickness="0"
diff --git a/PettingZoo/UI/Tab/Subscriber/SubscriberViewModel.cs b/PettingZoo/UI/Tab/Subscriber/SubscriberViewModel.cs
index 7a9ee8a..99b91fa 100644
--- a/PettingZoo/UI/Tab/Subscriber/SubscriberViewModel.cs
+++ b/PettingZoo/UI/Tab/Subscriber/SubscriberViewModel.cs
@@ -1,14 +1,16 @@
 using System;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
+using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
 using System.Windows.Input;
+using System.Windows.Threading;
 using PettingZoo.Core.Connection;
 using PettingZoo.Core.Rendering;
 using PettingZoo.WPF.ViewModel;
 
-// TODO visual hint of where the last read message was when activating the tab again
+// TODO if the "New message" line is visible when this tab is undocked, the line in the ListBox does not shrink. Haven't been able to figure out yet how to solve it
 
 namespace PettingZoo.UI.Tab.Subscriber
 {
@@ -18,7 +20,7 @@ namespace PettingZoo.UI.Tab.Subscriber
         private readonly ITabFactory tabFactory;
         private readonly IConnection connection;
         private readonly ISubscriber subscriber;
-        private readonly TaskScheduler uiScheduler;
+        private readonly Dispatcher dispatcher;
         private ReceivedMessageInfo? selectedMessage;
         private readonly DelegateCommand clearCommand;
         private readonly TabToolbarCommand[] toolbarCommands;
@@ -27,6 +29,8 @@ namespace PettingZoo.UI.Tab.Subscriber
         private readonly DelegateCommand createPublisherCommand;
 
         private bool tabActive;
+        private ReceivedMessageInfo? newMessage;
+        private Timer? newMessageTimer;
         private int unreadCount;
 
 
@@ -47,6 +51,14 @@ namespace PettingZoo.UI.Tab.Subscriber
             }
         }
 
+
+        public ReceivedMessageInfo? NewMessage
+        {
+            get => newMessage;
+            set => SetField(ref newMessage, value);
+        }
+
+
         public string SelectedMessageBody =>
             SelectedMessage != null
                 ? MessageBodyRenderer.Render(SelectedMessage.Body, SelectedMessage.Properties.ContentType)
@@ -70,8 +82,8 @@ namespace PettingZoo.UI.Tab.Subscriber
             this.tabFactory = tabFactory;
             this.connection = connection;
             this.subscriber = subscriber;
-            
-            uiScheduler = TaskScheduler.FromCurrentSynchronizationContext();
+
+            dispatcher = Dispatcher.CurrentDispatcher;
 
             Messages = new ObservableCollection<ReceivedMessageInfo>();
             clearCommand = new DelegateCommand(ClearExecute, ClearCanExecute);
@@ -116,12 +128,14 @@ namespace PettingZoo.UI.Tab.Subscriber
 
         private void SubscriberMessageReceived(object? sender, MessageReceivedEventArgs args)
         {
-            RunFromUiScheduler(() =>
+            dispatcher.BeginInvoke(() =>
             {
                 if (!tabActive)
                 {
                     unreadCount++;
                     RaisePropertyChanged(nameof(Title));
+
+                    NewMessage ??= args.MessageInfo;
                 }
 
                 Messages.Add(args.MessageInfo);
@@ -140,22 +154,39 @@ namespace PettingZoo.UI.Tab.Subscriber
         }
 
 
-        private void RunFromUiScheduler(Action action)
-        {
-            _ = Task.Factory.StartNew(action, CancellationToken.None, TaskCreationOptions.None, uiScheduler);
-        }
-
-
         public void Activate()
         {
             tabActive = true;
             unreadCount = 0;
 
             RaisePropertyChanged(nameof(Title));
+
+            if (NewMessage == null) 
+                return;
+
+            newMessageTimer?.Dispose();
+            newMessageTimer = new Timer(
+                _ =>
+                {
+                    dispatcher.BeginInvoke(() =>
+                    {
+                        NewMessage = null;
+                    });
+                },
+                null,
+                TimeSpan.FromSeconds(5),
+                Timeout.InfiniteTimeSpan);
         }
 
         public void Deactivate()
         {
+            if (newMessageTimer != null)
+            {
+                newMessageTimer.Dispose();
+                newMessageTimer = null;
+            }
+
+            NewMessage = null;
             tabActive = false;
         }
     }
@@ -165,6 +196,20 @@ namespace PettingZoo.UI.Tab.Subscriber
     {
         public DesignTimeSubscriberViewModel() : base(null!, null!, null!, new DesignTimeSubscriber())
         {
+            for (var i = 1; i <= 5; i++)
+                Messages.Add(new ReceivedMessageInfo(
+                    "designtime", 
+                    $"designtime.message.{i}", 
+                    Encoding.UTF8.GetBytes(@"Design-time message"), 
+                    new MessageProperties(null)
+                    {
+                        ContentType = "text/fake",
+                        ReplyTo = "/dev/null"
+                    }, 
+                    DateTime.Now));
+
+            SelectedMessage = Messages[2];
+            NewMessage = Messages[2];
         }
         
         
diff --git a/PettingZoo/UI/Tab/Subscriber/SubscriberViewStrings.Designer.cs b/PettingZoo/UI/Tab/Subscriber/SubscriberViewStrings.Designer.cs
index 11f6be5..38af1ff 100644
--- a/PettingZoo/UI/Tab/Subscriber/SubscriberViewStrings.Designer.cs
+++ b/PettingZoo/UI/Tab/Subscriber/SubscriberViewStrings.Designer.cs
@@ -96,6 +96,15 @@ namespace PettingZoo.UI.Tab.Subscriber {
             }
         }
         
+        /// <summary>
+        ///   Looks up a localized string similar to New messages.
+        /// </summary>
+        public static string LabelNewMessages {
+            get {
+                return ResourceManager.GetString("LabelNewMessages", resourceCulture);
+            }
+        }
+        
         /// <summary>
         ///   Looks up a localized string similar to Body.
         /// </summary>
diff --git a/PettingZoo/UI/Tab/Subscriber/SubscriberViewStrings.resx b/PettingZoo/UI/Tab/Subscriber/SubscriberViewStrings.resx
index 459982b..e0d0afa 100644
--- a/PettingZoo/UI/Tab/Subscriber/SubscriberViewStrings.resx
+++ b/PettingZoo/UI/Tab/Subscriber/SubscriberViewStrings.resx
@@ -112,10 +112,10 @@
     <value>2.0</value>
   </resheader>
   <resheader name="reader">
-    <value>System.Resources.ResXResourceReader, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+    <value>System.Resources.ResXResourceReader, System.Windows.Forms, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
   </resheader>
   <resheader name="writer">
-    <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+    <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
   </resheader>
   <data name="CommandClear" xml:space="preserve">
     <value>Clear</value>
@@ -129,6 +129,9 @@
   <data name="DeliveryModePersistent" xml:space="preserve">
     <value>Persistent</value>
   </data>
+  <data name="LabelNewMessages" xml:space="preserve">
+    <value>New messages</value>
+  </data>
   <data name="PanelTitleBody" xml:space="preserve">
     <value>Body</value>
   </data>
diff --git a/PettingZoo/UI/Tab/Undocked/UndockedTabHostViewModel.cs b/PettingZoo/UI/Tab/Undocked/UndockedTabHostViewModel.cs
index 9c139bc..bd46f75 100644
--- a/PettingZoo/UI/Tab/Undocked/UndockedTabHostViewModel.cs
+++ b/PettingZoo/UI/Tab/Undocked/UndockedTabHostViewModel.cs
@@ -8,7 +8,7 @@ using PettingZoo.WPF.ViewModel;
 
 namespace PettingZoo.UI.Tab.Undocked
 {
-    public class UndockedTabHostViewModel : BaseViewModel
+    public class UndockedTabHostViewModel : BaseViewModel, ITabActivate
     {
         private readonly ITabHost tabHost;
         private readonly ITab tab;
@@ -51,6 +51,17 @@ namespace PettingZoo.UI.Tab.Undocked
         {
             tabHost.UndockedTabClosed(tab);
         }
+
+
+        public void Activate()
+        {
+            (tab as ITabActivate)?.Activate();
+        }
+
+        public void Deactivate()
+        {
+            (tab as ITabActivate)?.Deactivate();
+        }
     }
 
 
diff --git a/PettingZoo/UI/Tab/Undocked/UndockedTabHostWindow.xaml.cs b/PettingZoo/UI/Tab/Undocked/UndockedTabHostWindow.xaml.cs
index 21ac421..1ea5fa5 100644
--- a/PettingZoo/UI/Tab/Undocked/UndockedTabHostWindow.xaml.cs
+++ b/PettingZoo/UI/Tab/Undocked/UndockedTabHostWindow.xaml.cs
@@ -1,5 +1,7 @@
-using System.Windows;
+using System;
+using System.Windows;
 using System.Windows.Controls;
+using System.Windows.Threading;
 
 namespace PettingZoo.UI.Tab.Undocked
 {
@@ -30,6 +32,16 @@ namespace PettingZoo.UI.Tab.Undocked
             {
                 viewModel.WindowClosed();
             };
+
+            Activated += (_, _) =>
+            {
+                viewModel.Activate();
+            };
+
+            Deactivated += (_, _) =>
+            {
+                viewModel.Deactivate();
+            };
         }
 
         private void Toolbar_Loaded(object sender, RoutedEventArgs e)