( It ( ( includes ( ( ( ( ( galaxies , ) ( star clusters ) ) , ) and ) nebulae ) ) . ) )
(ROOT (S (NP (PRP It)) (VP (VBZ includes) (NP (NP (NNS galaxies)) (, ,) (NP (NN star) (NNS clusters)) (, ,) (CC and) (NP (NN nebulae)))) (. .)))
It includes galaxies, star clusters, and nebulae.
(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))))))))) (. .)))