After centuries of mapping the human body in ever-finer detail, scientists are still making discoveries. Here we are, in 2025, and a previously unknown cellular structure that could be vital to our health has just been added to the anatomy books.
The membrane-bound organelle appears to play a huge role in helping cells sort, discard, and recycle their contents. It’s called a hemifusome, and a team of scientists says it could shed new light on disease.
“This is like discovering a new recycling center inside the cell,” said biophysicist Seham Ebrahim of the University of Virginia. “We think the hemifusome helps manage how cells package and process material, and when this goes wrong, it may contribute to diseases that affect many systems in the body.”
Not only that, the discovery helps us better understand the turnover and trafficking of compounds vital to the continuing function of our cellular machinery.
Related: Scientists Just Discovered a New Cell. It Was Predicted 100 Years Ago.
Cells like those making up a human body are highly complex, making it difficult to tease apart the fine structures responsible for their many processes. Even using highly sensitive technologies such as electron microscopy, samples need to be contained in a vacuum, which makes a mess of biological materials.
In recent years, however, a technique has emerged that allows us to probe biological samples almost down to atomic scales in three dimensions.
It’s called cryogenic electron tomography, or cryoET. Samples are frozen in a cryogenic medium too quickly for ice crystals to form and damage the fragile tissue; then scientists can study the material at high resolution, firing a beam of electrons through the sample to take a series of two-dimensional images.
Together, these two-dimensional slices can be used to create a three-dimensional reconstruction of the specimen detailed enough to reveal the internal structure of cells and molecules in high resolution.
This is the technique a team of researchers used to study different kinds of mammalian tissue – monkey, human, rat, and mouse. In all four of the cell types they studied they found multiple sacs that facilitate the formation of pairs of vesicles divided by a wall called a hemifusion diaphragm.
These vesicles, the researchers say, act a bit like sorting receptacles.
“You can think of vesicles like little delivery trucks inside the cell,” Ebrahim explains. “The hemifusome is like a loading dock where they connect and transfer cargo. It’s a step in the process we didn’t know existed.”
The researchers performed experiments with gold nanoparticles and cultured human cells to determine whether the way hemifusomes take up materials from their surroundings is similar to what has been observed in other cells. Interestingly, it appears that hemifusomes behave differently.
More work needs to be done to figure out what the organelle does, how it does it, and how it fits into the bigger picture of cellular machinery.
Further research could also reveal the role hemifusomes play in disease, since an inability to process cellular cargo properly can cause significant health setbacks.
“We’re just beginning to understand how this new organelle fits into the bigger picture of cell health and disease. It’s exciting because finding something truly new inside cells is rare – and it gives us a whole new path to explore,” Ebrahim says.
“Now that we know hemifusomes exist, we can start asking how they behave in healthy cells and what happens when things go wrong. That could lead us to new strategies for treating complex genetic diseases.”
The research has been published in Nature Communications.
