There’s a long history of researchers doing some fucked up experiments in the name of science. While this is well known, scientists are more tight-lipped about the results of those experiments, many of which were actually scientifically groundbreaking.

Today, most modern scientists are bound by the Nuremberg Code, a set of ethical rules developed when the Nazi medical atrocities went public. But back in the day, everything and everyone was fair game. Here’s a look at some super-immoral studies and their uncomfortably valuable results.

1. Little Albert Experiment

The “Little Albert” experiment was named, predictably, after a baby named Albert who was the center of this cruel — yet fruitful — experiment on inducing fear in children. John B. Watson, a researcher at Johns Hopkins University, together with his graduate student Rosalie Rayner, published their results in the Journal of Experimental Psychology in 1920. They wanted to know whether it was possible to condition a phobia into a child. Spoiler alert: it totally is.

In the experiment, Little Albert was placed in a room with a regular white lab rat, which he had no problem playing with. Next, the experimenters made a loud sound every time Albert reached for the rat — which, not surprisingly, caused him to cry out in fear. Over time, Albert would recoil in fear every time he saw the rat, even in the absence of the loud sound. They later found that Albert had generalized his fear to include other furry objects, including a dog, a sealskin coat, and a man dressed as Santa Claus.

The results of this experiment solidified what psychologists had begun to understand about classical conditioning with Pavlov’s initial experiments on dogs: the triggers for fear — together with other “innate” emotional responses — could be learned.

The American Psychological Association reports that Albert was, in fact, a nine-month-old named Douglas whose mother was employed as a wet nurse at a campus hospital and received $1 for her child’s participation in Watson’s experiment. The fear conditioning the baby went through was never reversed.

2. HeLa Cells

HeLa cells, the oldest and most commonly used cell line in research, are ubiquitous in the pages of academic journals. Unlike most cell types, which die after a few days, these cells are immortal and multiply indefinitely. Their contributions to science are countless: They were crucial in developing the polio vaccine and are used today in research on AIDS, cancer, and drug testing. But as much as we sing the cells’ praises, we rarely acknowledge their controversial roots: The original cells were taken from a patient named Henrietta Lacks without her knowledge or consent.

Lacks arrived at Johns Hopkins Hospital in February 1951 complaining of a pain in her abdomen, which eventually turned out to be a cervical cancer tumor. While she was receiving radioactive treatment for her cancer, which involved surgery to sew radium tubes into place, her surgeons removed healthy and cancerous sections of her cervix without telling her. These cells were eventually given to Dr. George Gey, who went on to study and cultivate the immortal cells. Lacks died of her cancer eight months later, and her family didn’t learn that her cells had been removed until the 1970s, when scientists from around the world began calling the family to learn more about their unique genetics.

3. Holmesburg Prison Trials

When tretinoin, a derivative of vitamin A, was first marketed as Retin-A in 1969, it was praised as a miracle treatment for acne. It’s still the world’s leading acne treatment today, it’s on the World Health Organization’s list of essential medicines, and it’s used to treat acute promyelocytic leukemia. Pretty powerful stuff. What most people don’t know is that it came at a pretty steep human cost.

It was discovered by Dr. Albert M. Kligman, a dermatologist at the University of Pennsylvania, after years of testing substances on the backs of prisoners at Holmesburg Prison in Philadelphia as early as 1951. “All I saw before me were acres of skin,” said Kligman in a 1966 newspaper interview. “It was like a farmer seeing a field for the first time.” According to a history of the experiments written by Allen M. Hornblum, who visited Holmesburg twenty years after Kligman’s testing began, the jail was packed with shirtless prisoners whose backs were striped with gauze, adhesive tape, and scars from biopsies.

To be fair, there was no law against scientific testing on human prisoners in the ‘50s and ‘60s, but by withholding detailed information about the experiments from the prisoners, Kligman is considered to have broken the first law in the Nuremberg Code: The voluntary consent of the human subject is absolutely essential. Not that it would’ve mattered much to the inmates, who were being offered anywhere from $10 to $300 a day, depending on the experiment.

4. The Milgram Experiments

“Could it be that Eichmann and his million accomplices in the Holocaust were just following orders? Could we call them all accomplices?” These are the questions Yale social psychologist Stanley Milgram asked when the Nazi war atrocities were made public. They went on to form the basis of his famously controversial experiments on obedience to authority figures, which were first published in the Journal of Abnormal Social Psychology in 1963.

In the experiments, volunteers were first paired with another person who was actually a confederate of Milgram’s. The pairs were then asked to draw lots to determine their roles — either “teacher” or “learner” — but the experiment was rigged so that the volunteer was always the teacher. The learner would then be placed in a room and hooked up to several electrodes. The teacher would join an “experimenter” — an actor dressed in a lab coat — in a separate room and presented with an electric shock generator.

The experimenter instructed the teacher to first teach the learner a series of word pairs then test his student: Every time the learner made a mistake, the teacher was told to administer an electric shock, each more intense than the last. Of course, there weren’t any real shocks involved, but the learner in the other room responded by screaming in pain every time.

Milgram hoped these experiments would shed light on what had happened among Nazi officers during the war. Although participants showed clear signs of distress once they started to hear their learners cry out in pain, many of them didn’t stop. In his first round of experiments, 65 percent of participants administered shocks up to the highest level. His data pointed to one terrifying conclusion: Ordinary people will indeed be obedient to authority, even to the point of killing a fellow human being.

5. Stanford Prison Experiment

The US Office of Naval Research funded the Stanford Prison Experiment, hoping it would identify the causes of conflict between prison guards and prisoners. In the studies, which took place at Stanford University in 1971, participants were randomly assigned the role of “prisoner” or “prison guard” and had to commit to the role for the duration of the experiment. While the experiment was meant to last two weeks, lead researcher Philip Zimbardo had to cut it short after six days. Participants took their roles way too seriously, and things quickly got out of hand.

Prison guards were told they couldn’t physically harm the prisoners, but they could say things to control them psychologically. Within days, guards were referring to prisoners by number instead of name to induce depersonalization. They had arbitrary status systems among them, and they even began forcing prisoners to take off their clothes or sleep on the concrete. By the time the experiment ended, Zimbardo had, like Milgram, revealed a difficult-to-stomach truth about human nature: Ordinary people were incredibly impressionable when faced with an authority figure, especially one supported by a social or cultural institution.

6. Gene Editing in Embryos

Unethical testing isn’t just a thing of the past. Earlier this year, Chinese scientists reported in the online journal Protein and Cell that they had successfully performed germline modification — on human embryos. These days, the ethics of human embryo testing is becoming increasingly hazy. While it’s still not considered acceptable among Western scientists, the field’s potential to change the face of medicine consistently threatens to reopen the debate.

If scientists manage to perfect gene editing in embryos, it’ll completely revolutionize genetics as we know it. It would effectively allow us to correct devastating genetic diseases in a babies before they’re even born. The research team behind the discovery successfully used “pre-implantation embryos” — which can’t result in a live birth — to modify a gene responsible for the blood disorder β-thalassemia using CRISPR/Cas9 technology. Western scientists have used this system successfully in animal models, but the Chinese study represents — as far as we know — the first time it’s been used in humans.