To reproduce run following code



import javafx.application.Application;
import javafx.beans.property.SimpleObjectProperty;
import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;
import javafx.beans.value.ObservableValue;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.scene.Group;
import javafx.scene.Node;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.layout.FlowPane;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Rectangle;
import javafx.stage.Stage;
import javafx.util.Callback;


/**
 *
 * @author javafx
 */
public class Test1 extends Application {

    public static void main(String[] args) {
        Application.launch(args);
    }

    private Parent getContent() {
        Pane pane = new HBox();
        TreeItem<String> root = new TreeItem<String>("ROOT", new Rectangle(20, 20, Color.CHOCOLATE));
        root.setExpanded(true);
        TreeItem<String> firstBrunch = new TreeItem<String>("brunch 1");
        firstBrunch.setExpanded(true);
        firstBrunch.getChildren().addAll(new TreeItem<String>("first item"), new TreeItem<String>("second item", new Rectangle(20, 20, Color.DARKGREY)));
        root.getChildren().addAll(firstBrunch);
        TreeItem<String> secondBrunch = new TreeItem<String>("brunch 2");
        secondBrunch.getChildren().addAll(new TreeItem<String>("first item"), new TreeItem<String>("second item", new Rectangle(20, 20, Color.DARKGREY)));
        root.getChildren().addAll(secondBrunch);
        TreeView tree = new TreeView(root);
        tree.setFocusTraversable(false);
        tree.setMaxSize(130,140);
        pane.getChildren().add(tree);
        return pane;
    }

    public void start(Stage stage) {
        stage.setX(100);
        stage.setY(100);
        stage.setWidth(700);
        stage.setHeight(700);
        Scene scene = new Scene(getContent());
        stage.setScene(scene);
        stage.show();
    }
    
}