A.I. Is Finding Sperm Where Doctors Couldn’t

New technology may make it easier for men with extremely low sperm counts to have biological children.

By Andrew Zaleski

Dolphin Carries Dead Calf in What Experts Call Grieving

Footage posted by a conservancy group offers an unusual glimpse of a common behavior by dolphins that often goes unobserved.

By Sopan Deb

Trump Signs Executive Order Calling for Fewer Childhood Vaccines

It is not clear whether the order, the president’s third to address the topic in less than a year, has any legal power.

By Apoorva Mandavilli and Dani Blum

Summer’s Strongest Meteor Shower Is Peaking. Here’s How to Watch.

The Perseids will be most active on Wednesday into Thursday morning, on the moonless night after a total solar eclipse.

By Katrina Miller

‘Like a Bomb Going Off’: Wildfire Forces Evacuation of 20,000 People in Canada

The Bald Range fire has burned more than 25,000 acres in British Columbia. At one point, the fire spread more than 2,000 acres in about an hour, officials said.

By Mark Walker and Ishani Desai

Butterflies Take Flight in Face of Climate Change and Extreme Weather

In 32 of the countries included in a recent study, at least a quarter of the native butterfly species had moved to new areas.

By Annie Roth

F.D.A. Moves Toward Tighter Restrictions on Food Ingredients

A proposed rule would require companies to notify the agency about ingredients they are using, but it is unclear if the agency has the resources to vet them all.

By Alice Callahan and Dani Blum

Major Quake Hits Colombia, Killing at Least 111

Rescue crews and regular people searched for survivors, and the death toll was likely to rise. More than 1,500 homes were damaged, the president said.

By Julie Turkewitz, Genevieve Glatsky and Michael Levenson

100 Animals and Plants Just Got Some Much-Needed Help

A new fund called the Phoenix Species Project will provide $200 million to help pull imperiled wildlife back from the brink of extinction.

By Catrin Einhorn

Trump’s Vision for A.I. Dominance Comes With Major Air Pollution

The president’s push for data centers is driving a boom in gas-burning power plants. Texas is leading the way.

By Hiroko Tabuchi

Why Are More Young Women Developing Heart Disease?

Rates are on the rise, but prevention is possible. Here’s what experts recommend.

By Nina Agrawal

The U.S. Relies on Family Caregivers. Millions of Them Are Kids.

The modern health care system requires the work of caregiving to fall to whoever else lives in a household — even if they’re kids.

By Helen Ouyang and Stephanie Sinclair

Global Health

An Invasive Mosquito Is Spreading With Alarming Speed, Threatening Africa’s Cities

The malaria-carrying mosquito is resistant to all insecticides. Scientists are scrambling to find ways to blunt the risk.

By Stephanie Nolen