( It ( ( contains ( ( ( ( ( ( star clusters ) , ) nebulae ) , ) and ) galaxies ) ) . ) )
(ROOT (S (NP (PRP It)) (VP (VBZ contains) (NP (NP (NN star) (NNS clusters)) (, ,) (NP (NN nebulae)) (, ,) (CC and) (NP (NNS galaxies)))) (. .)))
It contains star clusters, nebulae, and galaxies.
(ROOT (S (NP (DT A) (NN galaxy)) (VP (VBZ is) (VP (RBS best) (VBN described) (PP (IN as) (NP (NP (DT a) (NN cluster)) (PP (IN of) (NP (NP (NNS billions)) (PP (IN of) (NP (NNS stars))))))))) (. .)))