At the open

Investors are still in holiday weekend mode. The Dow opened down nearly 100 points. The Nasdaq and S&P 500 also opened lower.

Here’s what you need to know:

• North Korea said it successfully tested a hydrogen bomb over the weekend — the most powerful weapon it’s ever tested. President Trump condemned the event, saying that North Korea continues “to be very hostile and dangerous” to the U.S.
• President Trump is expected to end DACA, the Obama-era program that protects young undocumented immigrants from deportation.
• Lego, a.k.a. your childhood icon, is cutting nearly 8% of its workforce as it tries to revamp its strategy.
• Big news for the aerospace industry: United Technologies announced plans to buy Rockwell Collins for $23 billion.