( ( ( ( ( ( Classical physics ) ( ( rules ( the world ) ) ( that ( ( most ( of us ) ) ( are ( familiar with ) ) ) ) ) ) , ) but ) ( ( in ( ( the world ) ( of ( the atom ) ) ) ) ( , ( ( quantum mechanics ) ( is ( necessary ( to ( explain ( ( the observations ) ( scientists ( routinely ( see ( in ( the laboratory ) ) ) ) ) ) ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (JJ Classical) (NNS physics)) (VP (VBZ rules) (NP (DT the) (NN world)) (SBAR (IN that) (S (NP (NP (JJS most)) (PP (IN of) (NP (PRP us)))) (VP (VBP are) (ADJP (JJ familiar) (PP (IN with)))))))) (, ,) (CC but) (S (PP (IN in) (NP (NP (DT the) (NN world)) (PP (IN of) (NP (DT the) (NN atom))))) (, ,) (NP (NN quantum) (NNS mechanics)) (VP (VBZ is) (ADJP (JJ necessary) (S (VP (TO to) (VP (VB explain) (NP (NP (DT the) (NNS observations)) (SBAR (S (NP (NNS scientists)) (ADVP (RB routinely)) (VP (VBP see) (PP (IN in) (NP (DT the) (NN laboratory))))))))))))) (. .)))
Classical physics rules the world that most of us are familiar with, but in the world of the atom, quantum mechanics is necessary to explain the observations scientists routinely see in the laboratory.
(ROOT (S (NP (NNS Scientists)) (VP (VBP explain) (NP (DT the) (NN world)) (PP (VBN based) (PP (IN on) (NP (NNS observations))))) (. .)))