Get a category in magento - magento

Question

I have this kind of categories in magenta:
-MotoCross
->Parts1 ->sub-parts
->Parts2 ->sub-parts
->Parts3 ->sub-parts
-Quad
->Parts1 ->sub-parts
->Parts2 ->sub-parts
->Parts3 ->sub-parts
For now i have MotoCross and Quad printed on screen and their child (parts1,2,3) but I would like to have Part1 and them sub parts printed on screen.
I don't know how to do, see my code bellow:
---------------------------EDIT---------------------------
Now I have the current category categories, but i don't know how two have current category categories categories. You're still here ? :P
<?php
$object = new Mage_Catalog_Block_Navigation();
$actualCategoryId = $object->getCurrentCategory()->getId();
$actualCategory = Mage::getModel('catalog/category')->load($actualCategoryId);
$subCategories = explode(',', $actualCategory->getChildren());
?>
<div id="categories_list">
<ol>
<?php
foreach ( $subCategories as $subCategoryId )
{
$category = Mage::getModel('catalog/category')->load($subCategoryId);
if ( $category->getIsActive() )
{ ?>
<li class="second_level_cat">
<?php
echo ''.$category->getName().' ';
?>
</li>
<?php
}
}
?>
</ol>
</div>
Thanks for your help.

Answer 1

It's something like this.
<div id="categories_list">
<ol>
<?PHP foreach ($catIds as $cid): ?>
<?PHP $_category = Mage::getModel('catalog/category')->load($cid); ?>
<?PHP if($_category->getLevel() == 2 ) : ?>
<li class="second_level_cat">
<a href="<?php echo $this->getCategoryUrl($_category) ?>"<?php if ($this->isCategoryActive($_category)): ?> class="current"<?php endif; ?>><?php echo $this->htmlEscape($_category->getName()) ?></a>
</li>
<?php
$cat = Mage::getModel('catalog/category')->load($_category->getId());
$childrens = $cat->getChildren();
if($childrens)
{
$childs=explode(",",$childrens);
foreach($childs as $child){
$cat_child = Mage::getModel('catalog/category')->load($child);
?>
<li class="third_level_cat">
<a href="<?php echo $this->getCategoryUrl($cat_child) ?>"<?php if ($this->isCategoryActive($cat_child)): ?> class="current"<?php endif; ?>><?php echo ucfirst(strtolower($this->htmlEscape($cat_child->getName()))) ?></a>
</li>
<?php
}
}
?>
<?php endif; ?>
<?php endforeach ?>
</ol>
</div>

Answer 2

Here is code
$cats = Mage::getModel('catalog/category')->load(2)->getAllChildren(); // 2 = Root Category
$catIds = explode(',',$cats);
Select Category :
<select id="_cid" name="_cid">
<?PHP foreach ($catIds as $cid){ ?>
<?PHP $_category = Mage::getModel('catalog/category')->load($cid); ?>
<?PHP if($_category->getLevel() == 3 ) { ?>
<option value="<?PHP echo $_category->getId() ?>"> <?PHP echo $_category->getName() ?></option>
<?PHP } ?>
<?PHP if($_category->getLevel() == 4 ) { ?>
<option value="<?PHP echo $_category->getId() ?>"> <?PHP echo $_category->getName() ?></option>
<?PHP } ?>
<?PHP } ?>
</select>