如果在WebView中按下back按钮，如何回到上一页?

I have an app in which I have a WebView where I display some websites. It works, clicking a link in the webpage goes to the next page in the website inside my app. But when I click the phone's back button, it takes me straight into my app. I want to go back to the previous page in the website instead. How can I do this? where I