Thiry-five year ago I walked into the New York Times to begin my first real job, initially covering international business and economics, and to mark the anniversary I’ve gone back and dug up some of the pieces over the decades that were particularly meaningful to me.

The Tiananmen Massacre

As Beijing bureau chief for The New York Times, I covered the Tiananmen democracy movement in the spring of 1989. Then on the night of June 3-4, 1989, I received a call that the Chinese Army was invading the capital. Roads were blocked, so I jumped on my bike and pedaled toward the gunfire and then watched the Chinese Communist Party massacre its citizens. Troops fired on the crowd that I was in, leaving my notebook stained with the sweat of fear and destroying any illusions I ever had about China’s government. I abandoned my bicycle in the chaos, ran three miles back home in the early morning hours, embraced my wife, called my worried editors to tell them that I was alive, and hammered out the story.

Children for Sale

I’ve often written over the years about sex trafficking, and the reason goes back to a trip I made to Cambodia in 1996. I found girls who had been kidnapped and locked in brothels, and interviewed a frightened 14-year-old who was awaiting the sale of her virginity to the highest bidder. The other girls tried to reassure her. It felt like 19th-century slavery — except that these girls would be dead of AIDS by their early 20s. I thought of my own kids, and I couldn’t unsee those brothels. I was also troubled by my own complicity: I walked out of the brothels with great quotes, knowing that I had a good front-page story but that those girls would never get out. I wondered if I had exploited those girls for my own purposes, as other men had, and I felt an obligation to continue to highlight the topic and push for an end to such modern slavery. It all started with this piece.

A Story Worth Billions

My most consequential article was a 1997 piece from India about children dying needlessly of diarrhea and other ailments. It was important not because I said anything particularly new, but because it resonated with two readers in Seattle who were then thinking about where to direct their philanthropy. They read the article over their morning coffee, and they say that it got them thinking about channeling their money into global health — and Bill and Melinda Gates have since invested billions in this area and helped save millions of lives. Alas, my understanding is that what galvanized them wasn’t my luminous prose but rather a small chart that ran with the article and showed causes of global child mortality. Lesson: Always go with the graphics and visuals! A copy of this article is exhibited in the foyer of the Bill and Melinda Gates Foundation headquarters.

Surgeons Transforming Lives

Sometimes the way you know that a girl has an obstetric fistula is her smell and the way she looks at you with humiliated, hopeless eyes. A fistula is a childbirth injury that leaves a woman or girl incontinent and leaking urine or feces or both. Victims often think that they have been cursed by God, and they are afraid to eat or drink because then the wastes will start trickling down their legs. Yet a $600 surgery can usually repair the damage and give them their lives back. The most dazzling smiles I’ve ever seen are on girls whose fistulas had just been repaired. I’ve written about fistulas regularly since 2002 and am delighted to see it get more attention, with organizations like the Fistula Foundation now playing a major role. I once interviewed and wrote about an Ethiopian woman who suffered a fistula as a 15-year-old and then, while recovering, began to help out in the operating room. The hospital was short-handed, Mamitu was smart and hard-working, and doctors gave her more and more responsibility. Eventually, she began doing fistula repairs herself and became a leading gynecological surgeon — even though she had never attended so much as elementary school. This is a piece I wrote in 2003 about fistulas in Ethiopia.

The Frustrations of Iraq

The run-up to the Iraq war was deeply frustrating for me, because I wrote again and again about the perils of invading Iraq and yet even many liberal journalists embraced the invasion. I made a scary trip to visit Iraq under Saddam Hussein and it was clear that Iraqis both A.) hated Saddam and B.) hated the idea of a U.S. invasion even more. Yet my reporting from Iraq got little traction; I felt like Sisyphus. I came to see that on issues that people have already thought about, like Iraq or the Middle East, Donald Trump or abortion, it’s very difficult to change minds; the power of a columnist is less to sway people’s views than it is to propel an issue onto the agenda. Here’s one of my warnings that disappeared without a ripple.

Genocide in Darfur

Beginning in 2004, I made about a dozen trips to report on the genocide then unfolding in the Darfur region of Sudan. The reporting was terrifying, and I spent day after day with a knot in my stomach, worried for my own safety and especially for that of my interpreter, driver and video journalist colleague. Once, we were detained in a room with a mural on the wall of a man being impaled with a spear through the stomach. On my trips I saw kids who had been shot, women who had been gang-raped, a man whose eyes had been gouged out, an old couple who had been set on fire. Darfur showed me the evil that humans are capable of — and the indifference of most of the international community. Yet the ordinary citizens of Darfur showed extraordinary strength, even as they were largely abandoned. I met some Darfuris who used bows and arrows to fight against warlords with machine guns mounted on pickups, and I’ll never forget the moral courage of women who spoke up after rape.

21st-Century Concentration Camps

Early in my career, I simply pounded out articles — sent by telex from Fiji or the Philippines, by crackly telephone line from Mongolia or North Korea, by secret courier from Poland under martial law. Over time, I’ve increasingly turned to other avenues for storytelling because images and video can be so much more powerful than words on a page. One example is a 2014 video I did with a colleague, Adam Ellick, about the Rohingya minority in Myanmar. I was on my annual win-a-trip journey with a university student, Nicole Sganga, and there was a dicey moment when we were at sea in a boat whose engine gave out — leaving us stuck with curfew approaching — and I wondered what I had gotten Nicole into (eventually the motor restarted, and we returned to shore with only a modest breach of curfew). Yet I also wanted to show Nicole how reporting can bring back powerful stories and provide an early warning of humanitarian catastrophes, in this case of the hatred against the Rohingya that would later erupt in a savage mass slaughter that I also covered. Here’s the video.

‘He’s Jesus Christ’

People sometimes ask how I stay optimistic when I cover war, genocide and poverty. The answer is simple: Side by side with the worst of humanity, you encounter the best. I’ve made repeated trips to the rebel-held Nuba Mountains of Sudan, where the government dropped bombs and starved villagers, and there I met an extraordinary human being, Dr. Tom Catena, who has devoted his life to providing medical care as the bombs fall around him. A Muslim paramount chief told me that “Dr. Tom,” as he is known, heals the sick and lets the lame walk — and thus “He’s Jesus Christ.” On one trip to the Nuba Mountains, I was sickened to visit an extended family that had lost six children to a bomb but also moved that Dr. Tom had managed to save three others. So I return from a war zone like that scarred by the pain I’ve witnessed, but also uplifted by the goodness, strength and decency shown by people like Dr. Tom — and actually feeling better about humanity.

5 Minutes, $25 and a New Life

Another reason for optimism: I have seen immense progress in my 35 years of covering the world. On my first travels to poor countries, as a law student, I was pained by the number of blind people I saw led around by their children or grandchildren. Many were blind from cataracts, and in 2015 I met a remarkable Nepali doctor, Sanduk Ruit, who has pioneered a way to perform five-minute cataract surgery without electricity or advanced facilities for only $25 a patient. He has personally performed more than 120,000 cataract surgeries. You cannot watch Dr. Ruit’s patients take off their bandages and smile giddily as they see clearly for the first time in many years without feeling a rush of warmth about our world.

An Innocent Man Facing Death?

Beginning in 2010, I wrote a number of times about a black man named Kevin Cooper who I believe was framed for murder by the San Bernardino County sheriff’s office in California, where he is now on death row. The articles didn’t get much traction or readership, but the more I reported on the subject the more aware I became that there are many people on death row after dubious convictions. So last year, with the help of Times colleagues who are experts in visual journalism, I conducted a thorough investigation of the Cooper case and published the results. We called on the authorities to allow advanced DNA testing in the case (Kamala Harris and Jerry Brown had previously refused to allow the testing). It may have been the longest opinion column The Times ever published. The upshot is that advanced DNA testing is now finally underway, and I’m praying that after 36 years in prison Cooper may finally get justice — along with those who framed him. Here’s the investigation.

— Nicholas Kristof has been a columnist for The New York Times since 2001.