Yesterday, President Donald Trump followed through on his campaign promise to crack down on illegal immigration by signing an executive action ordering the construction of a wall between the U.S. and Mexico. More directives are expected this week that will ramp up deportation of the estimated 11 million undocumented immigrants already living in the U.S. A team of legal scholars from the University of California, Irvine breaks down the four main groups of immigrants who are vulnerable to deportation and explains why some are more likely than others to be targeted.

With the world’s population projected to grow to almost 10 billion by 2050, there is an urgent need to figure out how to produce more food while reducing agriculture’s environmental impacts. Colorado State University ecologist Matthew Wallenstein describes one such strategy: harnessing the power of microbes to increase crop production.

Back on Wall Street, the Dow Jones Industrial Average hit a milestone yesterday after surpassing 20,000 for the first time. A “milestone” you say? Ohio State’s Jay Zagorsky says it’s meaningless.

And finally, you might have heard about “darknets,” the ominous-sounding parts of the internet where privacy and encryption rule. Roderick Graham and Brian Pitman from Old Dominion University discuss their exploration of what exactly people are using darknets for – there’s a lot less crime than you might expect.