( ( An organ ) ( ( is ( ( a structure ) ( composed ( of ( ( several ( different types ) ) ( of tissues ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT An) (NN organ)) (VP (VBZ is) (NP (NP (DT a) (NN structure)) (VP (VBN composed) (PP (IN of) (NP (NP (JJ several) (JJ different) (NNS types)) (PP (IN of) (NP (NNS tissues)))))))) (. .)))
An organ is a structure composed of several different types of tissues.
(ROOT (S (NP (DT A) (PRN (-LRB- -LRB-) (NP (NN n)) (-RRB- -RRB-)) (NN organ)) (VP (VBZ is) (NP (NP (DT a) (NN structure)) (SBAR (WHNP (WDT that)) (S (VP (VBZ is) (VP (VBN composed) (PP (IN of) (NP (NP (QP (CD one) (CC or) (JJR more)) (NNS types)) (PP (IN of) (NP (NNS tissues))))))))))) (. .)))
A(n) organ is a structure that is composed of one or more types of tissues.