( We ( ( ( see properly ) ( when ( ( all ( of ( ( these parts ) ( of ( the ( ( eye and ) brain ) ) ) ) ) ) ( are ( working together ) ) ) ) ) . ) )
(ROOT (S (NP (PRP We)) (VP (VBP see) (ADVP (RB properly)) (SBAR (WHADVP (WRB when)) (S (NP (NP (DT all)) (PP (IN of) (NP (NP (DT these) (NNS parts)) (PP (IN of) (NP (DT the) (NN eye) (CC and) (NN brain)))))) (VP (VBP are) (VP (VBG working) (ADVP (RB together))))))) (. .)))
We see properly when all of these parts of the eye and brain are working together.
(ROOT (S (NP (NNS Brain) (CC and) (NNS eyes)) (VP (VBP are) (S (NP (DT the) (NNS organs)) (VP (VB work) (PRT (RP together)) (S (VP (TO to) (VP (VB allow) (S (NP (PRP us)) (VP (TO to) (VP (VB see)))))))))) (. .)))