We meet local scientist and entrepreneur Adam Khan to talk about his latest invention that he hopes will usher in a new diamond age of electronics that will make the silicon chip obsolete. Watch web extra videos.

We revisit a story about two men playing in the ice sheets of Lake Michigan in Hyde Park on their daily swim. Elizabeth Brackett reports. Read an article about the risks of swimming in cold water.

Back in 2012, we met two men – Greg Lane and Andre DeMar – who regularly swam in Lake Michigan, including during frigid Chicago winters. We spoke with Andre DeMar today to find out if he still swims in the frigid waters. It turns out he does. In fact, he swam in Lake Michigan this morning as the outside temperatures hovered around -2 degrees – without windchill. Read an interview.

Israeli singer-songwriter David Broza joins us with a conversation and performance. Watch web extra performances.

The polar vortex made its unwelcome return today, causing delays and closings. Will tomorrow be a repeat? Paris Schutz has the story. Send us your severe weather photos here and we'll use them in our online slideshow.

WGN's Chief Meteorologist Tom Skilling talks about the city’s record low temperatures, and what we can expect over the next few days.

We break down the rules Illinois has outlined for medical marijuana, and some additional restrictions Mayor Rahm Emanuel and Ald. Ed Burke would like to impose in Chicago.

The Chicago Department of Public Health is ramping up its campaign to increase teenage HPV vaccination coverage. We talk vaccinations and disease prevention with the agency’s medical director, Dr. Julie Morita. Read an interview and view graphics on HPV.

Illinois is one of 25 states that have chosen to expand Medicaid under the Affordable Care Act. We head to DuPage County to check up on the massive changes taking place in the state's health care system.

We talk with Chicago comic Pat McGann fresh off his first appearance on the Late Show with David Letterman. Watch his performance.

We share what you had to say about pension reform and Cook County boot camp labor in tonight's viewer feedback.

It turns out pension reform could save $15 billion less than legislative leaders initially anticipated. An actuarial analysis done by the pension systems affected by this bill say the real savings will be $145 billion, rather than the $160 billion originally advertised. Read an article.

Joel Weisman and his panel of journalists discuss the week's top headlines.

The panelists turn the tables and ask Joel Weisman a few questions about his favorite memories of hosting The Week in Review for the past 36 years. Watch the web extra video.

A scavenger hunt, restaurant tour and winter activities; Chicago Tonight knows what’s going on this weekend.