Display all sub categories via phtml file

<div>
<?php
    $children = Mage::getModel('catalog/category')->getCategories(37);
    foreach ($children as $category):
        $category = Mage::getModel('catalog/category')->load($category->getId());
        echo '<li><a href="' . $category->getUrl() . '">' . $category->getName() . '</a></li>';
            $child = Mage::getModel('catalog/category')->getCategories($category->getId());
            foreach ($child as $cat):
                $cat = Mage::getModel('catalog/category')->load($cat->getId());
                echo '<li><a href="' . $cat->getUrl() . '">' . $cat->getName() . '</a></li>';
            endforeach;
    endforeach;
?>
</div>