case: user has many posts and post has many comments. we need user's posts with comments:
//Eloquent query:
Users::with('posts')->get();
models and relationships:
//In User model:
protected $with="comments"; //it is important
public function posts() {
$this->hasMany('App\Post');
}
//In Post Model:
public function comments() {
$this->hasMany('App\Comments');
}