What does it take to change the world for the better? On this week's show, TED speakers explore ideas on activism-what motivates it, why it matters, and how each of us can make a difference.

At 17, Ruby Sales witnessed the shooting of one of her fellow civil rights activists. She explains how despite the trauma, she went on to devote her life to fighting for social and racial justice.

As a lifelong activist, Dolores Huerta has learned how to use her voice to fight for social justice. She discusses the power that all of us have to demand justice and spark movements for change.

In the digital age, the power of the collective has led to movements such as #MeToo and Black Lives Matter. Jeremy Heimans discusses how we can continue to use "new power" to drive activism.

Sarah Corbett describes herself as an extreme introvert -- but she's also an activist. She discusses how alternate forms of activism allow people like her to participate in quietly powerful ways.

How do our present thoughts and actions affect the future? Futurist Angela Oguntala shares ideas on how imagining the future we want to see is the first step toward achieving it.