Immortalised cells are cells that have been genetically modified or have undergone spontaneous mutations that allow them to divide indefinitely. Unlike normal cells, which have a limited lifespan, immortalised cells continue to divide even after they have reached their normal division limit. Cancer cells are an example of immortalised cells, as they have the ability to divide indefinitely and form tumours. They can be grown in the laboratory for long periods of time, enabling scientists to study the cellular and molecular mechanisms involved in various diseases, which are also used to test the efficacy of new drugs and to develop new therapies. However, it is important to note that immortalised cells are not normal cells and may differ significantly from normal cells. Therefore, results obtained from immortalised cells should be interpreted with caution and confirmed by further studies. In short, immortalised cells are an important tool for research in cell and molecular biology, but their use must be carefully controlled to guarantee reliable and significant results.