http://stackoverflow.com/q/35346039/2051646

import kivy
kivy.require('1.9.0') # replace with your current kivy version !

from kivy.app import App
from kivy.lang import Builder
from kivy.uix.screenmanager import ScreenManager,Screen

Builder.load_string('''
<ScreenManagement>:
    ScreenOne:
    ScreenTwo:


<ScreenOne>:
    name: 'First'
    Button:
        text: 'screen 1, press me to switch to screen 2'
        on_press: app.root.current = 'Second'

<ScreenTwo>:
    name: 'Second'
    BoxLayout:
        orientation: 'vertical'
        NestedScreenManagement:
        Button:
            text: "Change nested screenmanager to nested screen 2, not working"
            on_press: root.NestedScreenManagement.current = 'SecondNested'

<NestedScreenManagement>:
    NestedScreenOne:
    NestedScreenTwo:

<NestedScreenOne>:
    name: 'FirstNested'
    id: screen2
    Button:
        text: 'this is a button on nested screen one, press to switch to nested screen 2'
        on_press: root.manager.current = 'SecondNested'


<NestedScreenTwo>:
    name: 'SecondNested'
    id: screen2
    Label:
        text: 'nested screen one'

''')


class ScreenManagement(ScreenManager):
    pass

class ScreenOne(Screen):
    pass

class ScreenTwo(Screen):
    pass

class NestedScreenManagement(ScreenManager):
    pass

class NestedScreenOne(Screen):
    pass

class NestedScreenTwo(Screen):
    pass

class MyApp(App):

    def build(self):
        return ScreenManagement()

if __name__ == '__main__':
    MyApp().run()