how to show parent categories and subcategories with posts?

thanks for reply, i already solve it myself. here is my code this only work for two level categories.

<?php
//get all categories then display all posts in each term
$taxonomy = 'category'; //change this name if you have taxonomy
$param_type = 'category__in';
$term_args=array(
  'orderby' => 'name',
  'order' => 'ASC'
);
$terms = get_terms($taxonomy,$term_args);
if ($terms) {

	foreach($terms as $term){ //this foreach is for top level
		if($term->parent == 0){
		echo '<h2>'.$term->name.'</h2>'; //get top level category name
$term_args=array(
  'orderby' => 'name',
  'order' => 'ASC',
  'child_of' => $term->term_id
);
$termss = get_terms($taxonomy,$term_args);
  foreach( $termss as $terms ) { //this foreach is for second level
    $args=array(
      "$param_type" => array($terms->term_id),
      'post_type' => 'post',
      'post_status' => 'publish',
      'posts_per_page' => -1,
      'caller_get_posts'=> 1
      );
    $my_query = null;
    $my_query = new WP_Query($args);
    if( $my_query->have_posts() ) {  ?>
      <div class="category section">
        <h3><?php echo 'Category '.$terms->name; //get second level category name?></h3>
        <ul>
        <?php
      while ($my_query->have_posts()) : $my_query->the_post(); ?>
        <li><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"><?php the_title(); //get posts title name?></a></li>
       <?php
      endwhile;
      ?>
      </ul>
      </div>
 <?php
    }}
  }
  }
}
wp_reset_query();  // Restore global post data stomped by the_post().
?>