Science is amazing, but it can involve doing some pretty weird stuff. Just in time for Halloween, here are seven science experiments that are creepy, scary, or just plain gross!

1. Scientist lets insect live inside her

The sand flea, also known as chigger flea, is pretty gross. It burrows permanently into the skin of a warm-blooded host—like a human—where it swells, defecates, and produces eggs, before dying 4-6 weeks later, still embedded in the skin. We know a lot about them, but until now, their sex lives have been shrouded in mystery. Not anymore: A researcher in Madagascar was so interested in sand flea development that she let one of the bugs live inside her foot for 2 months. Her intimate observations paid off: She figured out that the parasites most likely have sex when the females are already inside their hosts.

2. Blood of young mice rejuvenates old mice

There are a lot of different interpretations of vampires out there—some sparklier than others—but two things remain consistent: Vampires guzzle blood and they live forever. As it turns out, if you’re trying to stay young, you could do worse than start with the blood of young victims. Scientists interested in aging joined two mice together—one young, the other old—and studied the effects. Once its circulatory system was connected to that of a younger mouse, the old mouse experienced reversed aging in muscle and in the brain. Although it’s not quite time to start asking your kids for blood transfusions, researchers are keen to start clinical trials in humans.

3. Pinpointing where fear lives in the brain

Fear is a pretty universal emotion. But where does it come from? And what’s it like to truly be fearless? Researchers tried to answer the first question in 2011, when they tested a human patient, known anonymously as SM, who did not experience fear. SM had lesions on her amygdala, a part of the brain thought to be key to our experience of fear. They exposed her to snakes and spiders, took her to a haunted house, and had her watch scary movies. She showed—and felt no fear. That settles it, the researchers thought—the amygdala is key to the human fear response.

Then, in 2013, some of the same researchers tested SM again. This time, they had her inhale CO 2 , an experience that causes a feeling of asphyxiation. SM didn’t stay calm. Instead she had a panic attack, just like the other subjects in the experiment, both of whom also had damaged amygdalas. The findings made it clear that the amygdala isn’t the only part of the brain that processes fear—and that fear really is a universal emotion.

4. Shocking people to “death”

Stanley Milgram’s tests are some of the best known psychology experiments out there, and with good reason. In 1961, in the wake of the high-profile trial of Nazi war criminal Adolf Eichmann, Milgram set out to test our obedience to authority figures. The experiment was simple: Subjects were instructed to give a series of escalating electric shocks to a person in another room. The shocks started at 15 volts and ended at a massive 450 volts. Although the two were separated, the subjects could communicate with the person getting the shocks and hear their (faked) reactions, which included screaming, banging on the wall, and complaining of a heart condition. After a while, the person in the next room would stop responding completely. The subjects were not threatened or berated—if they expressed discomfort, they were simply instructed, a maximum of four times, to keep administering the volts. The results were shocking: Milgram found that a full 65% of the subjects, despite obvious discomfort, administered the final—and seemingly fatal—450-volt electric shock to the person in the next room.

5. Of birds, aggression, and Dick Cheney

Be careful how you treat birds this Halloween—they remember! Researchers in Seattle ran an interesting experiment on crows. They designated a caveman mask as dangerous, and a Dick Cheney mask as neutral. They wore the dangerous mask to net and capture crows, and wore Cheney when they felt like acting the good guy. As it turns out, crows don’t forget a face: Up to two-thirds of the birds in the area would become upset when they saw the dangerous mask and start scolding, mobbing, and dive-bombing the wearer, no matter who they were.

6. Reanimation with dead hearts

If you’re smart, you already have a plan for the zombie apocalypse and you’ve got your survival team already picked out (no Beths allowed.) As it turns out, reanimation may not be complete science fiction. Researchers in California were successfully able to transplant “dead,” nonbeating hearts into young baboons. Although each of the subjects eventually died, they say that their findings suggest that we should one day be able to transplant “dead” hearts into humans too.

7. Frankenmouse!

Remember this picture? Creatively dubbed “Earmouse,” this little guy was originally held up as evidence that genetic engineering had gone too far. In reality, a better name for him may have been Frankenmouse—he’s the product of simple stitching, not genetic engineering. Earmouse’s creators molded sterile, biodegradable mesh into the shape of a human ear, which they seeded with bovine cartilage cells. To grow the ear, they needed a power source, so they stitched the ear-shaped scaffold onto a nude mouse, a mouse with no immune system. Once it was stitched on, the mouse’s own blood vessels infiltrated the scaffold, nourishing the incipient ear. By the time the scaffold dissolved, the ear was sturdy enough to stand on its own—and thoroughly creeped everyone out.