What is the purpose of creating this universe?

This universe have so many things that we can feel and can't feel. What is the reason behind such a big creation? Allah states in His book: > "Who remember Allah while standing or sitting or [lying] on their > sides and give thought to the creation of the heavens and the earth, > [saying], "**Our Lord, You did not create this aimlessly; exalted are > You [above such a thing]**; then protect us from the punishment of the > Fire." [3:191] and it seems that everyone should have an understanding of the answer to this question then to be able to confess about it the way Allah expects from us, that the creation is not aimless. What's the Allah's purpose for this creation? What does the Holy Quran says about it?