( ( The ( attempt ( to ( ( ( understand and ) classify ) ( the ( many particles ) ) ) ) ) ) ( ( ( ( discovered ( ( led ( to ( the recognition ) ) ) ( that ( ( ( protons and ) neutrons ) ( ( are not ) ( fundamental particles ) ) ) ) ) ) but ) ( are ( made ( of ( ( smaller objects ) ( called quarks ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN attempt) (S (VP (TO to) (VP (VB understand) (CC and) (VB classify) (NP (DT the) (JJ many) (NNS particles)))))) (VP (VP (VBD discovered) (VP (VBN led) (PP (TO to) (NP (DT the) (NN recognition))) (SBAR (IN that) (S (NP (NNS protons) (CC and) (NNS neutrons)) (VP (VBP are) (RB not) (NP (JJ fundamental) (NNS particles))))))) (CC but) (VP (VBP are) (VP (VBN made) (PP (IN of) (NP (NP (JJR smaller) (NNS objects)) (VP (VBN called) (NP (NNS quarks)))))))) (. .)))
The attempt to understand and classify the many particles discovered led to the recognition that protons and neutrons are not fundamental particles but are made of smaller objects called quarks .
(ROOT (S (NP (NNS Protons) (CC and) (NNS neutrons)) (VP (VBP are) (VP (VBN made) (PP (IN of) (NP (NP (NNS quarks)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBP are) (NP (NP (JJ fundamental) (NNS particles)) (PP (IN of) (NP (NN matter))))))))))) (. .)))