Unable to load file inside folders in Codeigniter

I am working with Codeigniter,I want to load file inside folders but unable to get html/design in webpage,In other words,my following code is working (“header.php” exist inside “common” folder)

<?php
    $this->load->view('common/header');
?>

But following code is not working (move “header.php” inside “backend” folder,Where i am wrong ?

<?php
    $this->load->view('common/backend/header');
?>