I have a question...

Rating: 9/10 (5 June 2006)

I just want to say that i really like that movie.Excellent Sci-Fi story,breathtaking action,horrible and deadly never-seen-before creatures,great Sigourney Weaver, etc.I have watched "Aliens" when i was about 14 or 15 years old and it was pretty scary and really fascinating at the same time!I have seen it many times since and i never get bored of it.It is one of the best if not the best film ever created in this genre!
P.S. I have just one question-can somebody tell me please how these alien creatures had bred themselves before meeting the human race????????????? :) :) :)