NBC Nightly News with Brian Williams
Security stepped up for the Boston Marathon
More: http://nbcnews.to/1i8pjFm

Security stepped up for the Boston Marathon

More: http://nbcnews.to/1i8pjFm

SpaceX Falcon 9 rocket blasts off on mission to International Space Station

SpaceX Falcon 9 rocket blasts off on mission to International Space Station

JUST IN: 7.5-magnitude earthquake strikes Guerrero, Mexico, USGS says

JUST IN: 7.5-magnitude earthquake strikes Guerrero, Mexico, USGS says

JUST IN: Chelsea Clinton announces she is pregnant with her first child

JUST IN: Chelsea Clinton announces she is pregnant with her first child

BREAKING NEWS: 8 million Americans have now signed up for health insurance under the Affordable Care Act, President Obama says

BREAKING NEWS: 8 million Americans have now signed up for health insurance under the Affordable Care Act, President Obama says