The Environmental Protection Agency sampled a small number of Chicago homes and found higher levels of lead where water pipes were disturbed by street work and plumbing repairs. We have analysis. Read the EPA study.

Alan Dixon talks about 40 years of public service in his new book, The Gentleman from Illinois. Read an excerpt and watch web extra interviews with Dixon from WTTW's archives.

It’s the world’s most powerful digital camera and it sits atop the Blanco telescope in the Andes Mountains of Chile. But it was constructed on the campus of Fermilab in far west suburban Batavia. The Dark Energy Camera officially began its work on August 31 and has already captured some amazing images of outer space. Its real mission, though, is to help scientists figure out if so-called Dark Energy is responsible for the universe’s accelerating expansion. We learn how the camera is helping scientists unravel one of the greatest mysteries in the cosmos. Watch videos and view a slideshow.

Randall Wells, one of the world’s leading dolphin researchers, joins us to discuss the longest-running study of a wild dolphin population and his commitment to conservation. Read an interview and view a slideshow.

Chicago Tonight Correspondent Elizabeth Brackett is currently in Nairobi, not far from Westgate Shopping Mall, the site of a terrorist attack launched by Islamic radicals that killed dozens of shoppers and injured more than 170 people. Watch web extra interviews.

Looking back at a couple of influential dancers, and looking ahead to a weekend dance concert.

Still gathering stories on Janis Joplin's final Chicago-area performance...

Four suspects are in custody for the mass shooting in Chicago's Back of the Yards neighborhood. Paris Schutz has the latest.

We take a closer look at what happened the night of the Back of the Yards mass park shooting, and examine Chicago's persistent violence, with Felicia Davis, Mayor Rahm Emanuel's deputy chief of staff, and Chicago Tribune reporter Peter Nickeas.

Just months after closing 47 Chicago schools, Mayor Rahm Emanuel's plan to build or expand other schools has drawn fresh outrage from teachers and parents. Phil Ponce talks with Chicago Teachers Union President Karen Lewis and Chicago Board of Education Vice President Jesse Ruiz about the issue.

Though the historical handshake between President Barack Obama and Iranian President Hassan Rouhani didn’t happen at the United Nations luncheon today, there’s already speculation another opportunity may be on its way, and relations between the two countries could continue to thaw. We talk with Middle Eastern political expert, Marvin Zonis. View a timeline of U.S. and Iranian diplomatic relations.

At half an acre, the rooftop garden atop McCormick Place West is the largest in the entire region. We revisit the backstory behind this little-known space. Read an article.

Frank Lloyd Wright’s apprentice brought the Prairie School of Architecture to Europe. We take a look at the innovations of architect Barry Byrne with Vincent Michael, the author of The Architecture of Barry Byrne. Read a book excerpt and view a slideshow.

Another look at a truly unusual performance by Eric Clapton -- with additional photos.

All eyes are on the U.S. Senate as a potential government shutdown looms. Paris Schutz has more on what Sen. Dick Durbin and Illinois members of Congress are planning to do.