Tonight on PBS News Weekend, European leaders will join Volota Mer Zelensky for tomorrow's

high-stakes Oval Office meeting to present a united front.

Then how trouble getting a good night's sleep has become a public health emergency.

And one man's quest to capture dazzling images of fireflies

and raise awareness about the threats facing

these glowing symbols of summer.

I stumbled upon a forest with millions and millions of fireflies

synchronizing their flashes across vast expanses of the forest.

And there's been no looking back.

Good evening. I'm John Yang. The last time Ukrainian president, Volodemir Zelensky, was in the Oval Office,

things got heated as President Trump loudly berated him. But when he returns tomorrow, he'll have reinforcements.

At least a half dozen European leaders will join him in a high-profile display of unity.

After meeting with Russian President Vladimir Putin last week, Mr. Trump aligned himself with Russian positions.

That triggered European fears that Ukraine could be pressured into accepting a deal on Moscow's terms.

Today, Zelensky was in Brussels meeting with European Commission President Ursula

von der Leyen. Since the beginning of Russia's brutal invasion, Europe has been at Ukraine's side,

united, and we will support you for as long as it takes, for just and lasting peace.

It's very important that you are with us and that we speak to America and we speak together.

To look ahead to tomorrow's meeting, William Taylor, he's a distinguished fellow at the

Atlantic Council's Eurasia Center.

He's a former U.S. ambassador to Ukraine and was temporary head of mission there in the

first Trump term, later testifying in Mr. Trump's impeachment. Mr. Ambassador, this is going to be

...