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Imagine something small enough to float[br]on a particle of dust

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that holds the keys to understanding[br]cancer, virology, and genetics.

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Luckily for us,

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such a thing exists in the form [br]of trillions upon trillions

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of human lab-grown cells[br]called HeLa.

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Let's take a step back for a second.

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Scientists grow human cells in the lab[br]to study how they function,

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understand how diseases develop,

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and test new treatments without[br]endangering patients.

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To make sure that they can repeat[br]these experiments over and over,

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and compare the results [br]with other scientists,

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they need huge populations [br]of identical cells

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that can duplicate themselves [br]faithfully for years,

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but until 1951, all human cell lines[br]that researchers tried to grow

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had died after a few days.

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Then a John Hopkins scientist[br]named George Gey

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received a sample of [br]a strange looking tumor:

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dark purple, shiny, jelly-like.

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This sample was special.

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Some of its cells just kept dividing,

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and dividing,

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and dividing.

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When individual cells died,

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generations of copies took their place[br]and thrived.

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The result was an endless source of[br]identical cells that's still around today.

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The very first immortal human cell line.

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Gey labeled it "HeLa" after the patient[br]with the unusual tumor, Henrietta Lacks.

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Born on a tobacco farm in Virginia,

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she lived in Baltimore with her husband[br]and five children.

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She died of aggressive cervical cancer

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a few months after her tumorous cells[br]were harvested,

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and she never knew about them.

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So what's so special about the cells[br]from Henrietta Lacks

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that lets them survive[br]when other cell lines die?

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The short answer is[br]we don't entirely know.

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Normal human cells have built-in[br]control mechanisms.

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They can divide about 50 times[br]before they self destruct

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in a process called apoptosis.

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This prevents the propagation[br]of genetic errors

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that creep in after [br]repeated rounds of division.

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But cancer cells ignore these signals,[br]dividing indefinitely

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and crowding out normal cells.

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Still, most cell lines eventually die off,[br]especially outside the human body.

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Not HeLa, though, and that's the part[br]we can't yet explain.

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Regardless, when Dr. Gey realized he had[br]the first immortal line of human cells,

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he sent samples [br]to labs all over the world.

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Soon the world's first [br]cell production facility

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was churning out [br]6 trillion HeLa cells a week,

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and scientists put them to work[br]in an ethically problematic way,

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building careers and fortunes[br]off of Henrietta's cells

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without her or her family's consent,[br]or even knowledge until decades later.

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The polio epidemic was at its peak[br]in the early 50s.

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HeLa cells, which easily took up[br]and replicated the virus,

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allowed Jonas Salk to test his vaccine.

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They've been used to study diseases,

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including measles,

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mumps,

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HIV,

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and ebola.

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We know that human [br]cells have 46 chromosomes

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because a scientist working with HeLa[br]discovered a chemcial

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that makes chromosomes visible.

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HeLa cells themselves actually have[br]around 80 highly mutated chromosomes.

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HeLa cells were the first to be cloned.

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They've traveled to outer space.

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Telomerase,

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an enzyme that helps cancer cells evade[br]destruction by repairing their DNA,

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was discovered first in HeLa cells.

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In an interesting turn of fate,

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thanks to HeLa, we know that cervical[br]cancer can be caused by a virus called HPV

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and now there's a vaccine.

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HeLa-fueled discoveries have filled[br]thousands of scientific papers,

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and that number is probably even higher[br]than anyone knows.

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HeLa cells are so resilient that they [br]can travel on almost any surface:

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a lab worker's hand,

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a piece of dust,

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invading cultures of other cells [br]and taking over like weeds,

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countless cures, patents and discoveries[br]all made thanks to Henrieta Lacks.