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PBS NewsHour

The phytoplankton that brought Earth to life

4:43

Without the "billion billion billion" Prochlorococcus, a plant-like bacteria in the ocean, Earth would not have the oxygen we breathe today. But the more scientists study about these diverse organisms, the less they know, says Penny Chisholm, an oceanographer at MIT.

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PBS NewsHour

State of the Union 2016

PBS NEWSHOUR offers live coverage of President Obama's speech and the Republican response.

0:20

PBS NewsHour

PBS NewsHour Weekend

Premieres Saturday, September 7, 2013 at 6 p.m. ET.

0:30

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