Image: Dr. Patricia González Jiménez

Forget haunted houses and ghosts in the attic. This Halloween, some of the strangest creatures can be found somewhere much closer to home: inside a cell culture dish.

“I see dead people.”

Well… not quite.

At first glance, this image might look like something from a horror movie: a dark landscape filled with glowing green shapes, scattered red lights, and an eerie face staring back from the microscope. But there are no ghosts here.

These are cells.

In our laboratory, we work with L929 murine fibroblasts, a well-established mouse connective-tissue cell line. Using a Live/Dead assay, we can distinguish living cells from cells with compromised membranes. Calcein AM makes viable cells glow green, while Ethidium homodimer marks dead or membrane-compromised cells in red. The result is a fascinating snapshot of a microscopic world where cells grow, divide, interact, and die.

This isn’t just for show, it’s part of an ambitious project where we are building cellular automata and digital twins: computational models designed to reproduce and ultimately predict how cells behave under changing conditions. By learning from real experimental data, these virtual populations can help us understand cell growth, survival, interactions, and death. The long-term goal is to develop predictive tools that could contribute to research in cancer therapies, wound healing, tissue regeneration, and biomaterials, while potentially helping to reduce the need for animal experiments.

But biology rarely follows the script. In an ideal textbook experiment, cells grow predictably, reach a peak, and gradually decline. In real life, cells can suddenly die, survive unexpected conditions, or form strange spatial patterns. Sometimes, when you look through the microscope, cellular patterns can even resemble a monster staring back at you. And these surprises are scientifically valuable. Every unexpected result, strange cluster, and stubborn surviving cell gives us another clue about the complex rules governing living systems. And if your microscope ever shows you a monster…

Don’t panic. Take a picture. It might be science. 🔬🧟‍♂️