( ( One example ) ( ( is ( ( rain water ) harvesting ) ) . ) )
(ROOT (S (NP (CD One) (NN example)) (VP (VBZ is) (NP (NP (NN rain) (NN water)) (VP (VBG harvesting)))) (. .)))
One example is rain water harvesting.
(ROOT (S (NP (NP (CD One) (NN example)) (PP (IN of) (NP (NN matter)))) (VP (VBZ is) (NP (NN water))) (. .)))
One example of matter is water.