Scientists have found a way to reverse the process of cell division, previously thought to be unstoppable.
A cervical cancer cell dividing
The finding by US researchers could have important implications for cancer, which is caused by cells dividing uncontrollably.
Writing in Nature, the team explained how controlling a key protein can interrupt the process.
UK experts on cancer cell behaviour said the research aided understanding of how cells should divide.
Cell division occurs millions of times each day in the human body.
Each time, the cell is supposed to be in the prime of health - so any DNA damage has to be repaired first - and the 46 pairs of chromosomes in the cell have to be divided equally between its "daughters".
However, both of these things can go wrong in cancer cells.
In the lab, researchers from the Oklahoma Medical Research Foundation were able to control a protein called cyclin which normally plays a key role in instigating cell division before disappearing.
They inactivated it using a chemical, and then washed that chemical out of the cells.
This meant cell cycle went backwards, sending duplicate chromosomes back to the centre of the original cell, which had been thought impossible, rather than continuing the division process.
This appeared to be because the cyclin was still present in the cell when, under natural circumstances, it should not be.
But the team had to act at a particular point, or the intervention failed to reverse cell division.
The team say this suggests many other factors involved in regulating cell division.
Dr Gary Gorbsky, who led the research, said: "No-one has got the cell cycle to go backwards before now.
"This shows that certain events in the cell cycle that have long been assumed irreversible may, in fact, be reversible."
Professor Jonathon Pines, an expert in cancer cell division at the Gurdon Institute in Cambridge, said the research would not lead directly to new cancer treatments.
But he added: "It is useful for us to understand how the cell goes through the process of segregating the chromosomes."