Whether as a sun-seeking holidaymaker in the Mediterranean or as an intrepid voyager on an uncharted Arctic plain, humans are often on the move to new destinations. For many purposes and by many means we routinely journey across the surface of our planet, generating as we do so intersecting travel paths which intertwine like a tightly wound ball of yarn. Aided by the availability of low-cost airlines we have become the most well travelled generation that history has ever seen. Yet even in the current culture of accessible international transport links few of us will ever be able to boast that we have visited almost every country in the world.

Henrietta Lack is one individual, however, about whom such a lofty claim can be made with confidence. For Henrietta has travelled the globe several times over and continues to do so today. Not content with earthly locations, she has even been to space. Even more remarkably, she managed to be present at all of these locations simultaneously. And yet, she has been dead for 54 years and, during her short lifetime, she never once left the US state of Virginia. It sounds impossible, so how can this be the case?

As a young woman Henrietta developed a particularly aggressive form of cervical cancer. During treatment for the disease, her doctor, without her knowledge, took from her a small sample of the tumour. This sample was passed to Drs. George and Margaret Gey, two scientists whose specialist field was the culture of tissues, that is, the growing of cells in an artificial environment outside of the organism from which they originated. In practice, this means that the harvested cells are sustained in a culture dish in a laboratory and are said to be grown in vitro.

In contrast to previous attempts to culture human cells, Henrietta's cells grew readily in vitro. More significantly they also appeared to be immortal, growing for many generations beyond the finite lifespan typical of other human cells which the Geys and others had unsuccessfully tried to culture. With these cells the Geys had generated the first human cell-line which was soon to become known worldwide as the HeLa cell line the name a truncated version of its donor's.

The exciting potential that HeLa cells offered to the scientific community was reflected in the rapidity with which they then became distributed across the world. Within only a few years, HeLa cells were being routinely used in laboratories from Chile to Russia and at many points in-between. Still housed in the labs of countless nations, the current biomass of HeLa cells today far exceeds that which Henrietta was composed of in life and thus she has truly circumvented the globe in an unrivalled fashion.

The excitement with which HeLa cells were received by the scientific community was justified. Prior to HeLa cells, cells cultured in vitro often deteriorated too rapidly to be used to obtain meaningful results. Furthermore, methodical experimentation required that one has access to a plentiful and consistent source of test material. Thus the value of a cell-line is that it provides an indefinite supply of cells which when treated appropriately are invariant in terms of their genetic make-up and physical characteristics. This allows scientists to return time and time again to an identical source of cells which they can then manipulate to unravel the answer to numerous puzzles, such as how do cells divide? How do they communicate with one another? How do they die?

Accordingly, HeLA cells have proved to be the foundation of investigative work into the processes which occur in human cells. Almost all the current knowledge regarding the intricacies of human cellular composition, organisation and processing has been gleaned to some extent, from work on HeLa cells. They have proved to be the bedrock of cancer research by allowing scientists to unpick the genetic and biochemical processes which lead to the uncontrolled division of cells in cancerous growths. Additionally they were crucial in the development of polio vaccine by providing Jonas Salk with a means to generate enough raw viral material with which to design a vaccine. Viruses must infect living cells in order to replicate and prior to the HeLa line, generating sufficient quantities of virus in the lab had been very difficult. During various space missions HeLa cells have also been studied in conditions of zero gravity to investigate how fundamental cellular processes and metabolic pathways respond to the environment of space.

Henrietta Lack has thus been integral in two astonishing journeys. The first, a physical distribution of one woman's cells across the countries of the world. The second, a journey of intellect and learning, remarkable in the manner it has seen scientific knowledge and understanding advance. Both literally and scientifically, Henrietta Lack has broadened horizons.