( Phytoplankton ( ( are ( ( classified ( into groups ) ) ( by ( ( the type ) ( of ( pigments ( they ( use ( to ( perform photosynthesis ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Phytoplankton)) (VP (VBP are) (VP (VBN classified) (PP (IN into) (NP (NNS groups))) (PP (IN by) (NP (NP (DT the) (NN type)) (PP (IN of) (NP (NP (NNS pigments)) (SBAR (S (NP (PRP they)) (VP (VBP use) (S (VP (TO to) (VP (VB perform) (NP (NN photosynthesis)))))))))))))) (. .)))
Phytoplankton            are classified into groups by the type of pigments they use to perform            photosynthesis.
(ROOT (S (NP (NNP Phytoplankton)) (VP (VBP make) (NP (NP (NN food)) (PP (IN via) (NP (NN photosynthesis))))) (. .)))