After many years of study, no one knows how much sleep we need to function normally.

FORBES: Marketing

Mitochondria are tiny structures found in all cells in our bodies and produce most of the energy we need to function normally.

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It also takes into account UNESCO's deep and continuing concerns about journalist murders around the world because the profession's work is critical to providing us with the information we need to function as a civil society.

UNESCO: Freedom Page

They have developed a program that filters out the noise in much the same way that the human brain's reticular activating system filters out most of our sensual stimuli, and only passes on the information we need to function and survive.

ECONOMIST: MONITOR

We need to know how to function differently across many areas of the system: health, entitlements, pensions, transportation, energy, extraction, education, politics.

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And we also need the airports to function well so that people can move around from one city to another.

BBC: Is Brazil ready to host the 2014 World Cup?

We need to teach them that success is not a function of fame or P.

CNN: Transcript: Obama's State of the Union speech