Armed with a microscope and a high-speed camera, scientists have recorded microscopic footage of how a jellyfish stings its victims upon contact. The footage may also help explain why the jellyfish stings can be so painful.

The video footage, uploaded on YouTube channel Smarter Every Day, shows scientists from James Cook University in Australia observing and capturing the entire process of stinging. With them was Smarter’s host and founder Destin Sandlin who talked with toxinologist Dr. Jamie Seymour about the stinging process.

While some may regard the sting as allergic reaction brought about by the tentacles of the jellyfish, it appears to be anything but that.

Based on the microscopic slow motion video, it turns out the tentacles of jellyfishes have cell organelles known as nematocysts, which elongate every time it comes in close contact with a potential victim. These organelles in the jellyfish’s tentacles are hypodermic needles filled with venom that function like syringes, stinging the skin’s surface with toxins in an instant. They are, however, too small to be seen by the naked eye.

The footage showed a sea anemone being triggered by electricity from a nine-volt battery. The sea anemone and jellyfish, both cnidarians, have same stinging structures. As soon as it came near its target, the small hypodermic needles protruded and immediately shot its prey with venom.

The average deployment time of the nematocyst, or the time the needled was released and the venom was injected, is 11 milliseconds—a time leg that Dr. Seymour described as something that blew him away.

“We’ve never seen that before,” said Dr. Seymour in the video footage.

According to the National Health Service, largest publicly funded health service in the world, symptoms of a jellyfish sting include vomiting or nausea, diarrhea, abdominal pain, muscle spasms, tingling or numbness and swollen lymph nodes. For rare cases, it may bring about difficulties in breathing, coma and, worst, death after three minutes of having been stung.

Meanwhile, the National Science Foundation’s special report revealed that around 150 million people around the world are exposed to jellyfish every year. It also said that jellyfishes are important players in our marine ecosystem but are often underappreciated by our scientific community. In fact, jellyfish are helpful when it comes to disabling nuclear power plants by simply clogging the intake pipes. Though jellyfish swarms are also to blame partly for destroyed fish farms and fisheries, among other things.