How to style WPF tooltip like a speech bubble?

Use this Code:

<Window x:Class="WpfApplication2.MainWindow"    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"    xmlns:ed="http://schemas.microsoft.com/expression/2010/drawing"    x:Name="Window"    Title="MainWindow"    Width="640"    Height="480"><Window.Resources>    <Style x:Key="{x:Type ToolTip}" TargetType="ToolTip">        <Setter Property="OverridesDefaultStyle" Value="true" />        <Setter Property="HasDropShadow" Value="True" />        <Setter Property="Template">            <Setter.Value>                <ControlTemplate TargetType="ToolTip">                    <ed:Callout Name="Border"                                Width="{TemplateBinding Width}"                                Height="{TemplateBinding Height}"                                MinWidth="100"                                MinHeight="30"                                Margin="0,0,0,50"                                AnchorPoint="0,1.5"                                Background="{StaticResource LightBrush}"                                BorderBrush="{StaticResource SolidBorderBrush}"                                BorderThickness="1"                                CalloutStyle="RoundedRectangle"                                Fill="#FFF4F4F5"                                FontSize="14.667"                                Stroke="Black">                        <ContentPresenter Margin="4"                                          HorizontalAlignment="Left"                                          VerticalAlignment="Top" />                    </ed:Callout>                </ControlTemplate>            </Setter.Value>        </Setter>    </Style></Window.Resources><Grid>    <Button ToolTip="Hello" /></Grid>

this is the begining, now you have to play with it... enjoy!