Scientists have found a way to detect the earliest signs of cancer in a single human cell.
There are trillions of cells in the human body but a change in only one can lead to disease.
Certain genes are switched on when the cell becomes cancerous, allowing it to divide rapidly and grow out of control.
Coloured dyes that label these harmful genes could lead to new diagnostic tests.
A team at Albert Einstein College of Medicine in New York, US, made 11 dyes that stick to activated genes within cancerous cells.