Home buton and fragment

I would like to know why for exemple if i have 2 fragment. When the application start im on fragment 1 but i click on menu to fragment 2 then i press home button i go back to my app and the app display the fragment 1 ? Why it do not stay in fragment 2 ? i mean this is probably due to the fact that when i press home button the activity go on onpause -> onstop then i go back on the activity and oncreate is call again but how can i make that the applicvaiton ill remember the last fragment that i was on