You can't see them when you look in the mirror but, in case you didn't know, you are composed of 100-trillion cells.

The cells are really little. It would take 1,000 of them to cover the period at the end of this sentence.

Rebecca Skloot told several hundred men and women in the McManus Room of Westport Library all about the cell numerology Feb. 5 -- three days after her now-red-hot book, The Immortal Life of Henrietta Lacks, came out.

At the time of her appearance in Westport, Skloot's book had sold out at Barnes and Nobles store in town and on Her tome, a first book by an unknown writer, rocketed to No. 5 on the New York Times best-seller list Feb. 12.

Skloot got into cells early on during her Westport visit -- the first week of a four-month tour for this reason:

Cells are the book's stem-winder. In particular, a cell line generated from ones taken from Lacks' cancerous cervix when she was being treated in the segregated black ward at Johns Hopkin hospital in Baltimore in 1951. At the time, Lacks, a dirt-poor tobacco farm laborer from Clover, Va., was 31 and two of her five children, the babies, were in diapers.

Doctors took her cells, called HeLa (using the first two letters of Lacks' first and last names), and stored them in research labs. Since that time, they have been used in many medical breakthroughs for the last 60 years. But Lacks never knew about it, Skloot told Westporters,

"Doctors took her cells without asking. Those cells never died. They became one of the most important tools in medicine," Skloot said.

HeLa line speeded up approval of the Salk polio vaccine, leading to field trials and the pronouncement on April 12, 1955, that the vaccine worked -- was safe and effective.

That cleared the way to vaccinate millions, putting a big dent in polio epidemics that had the nation cringing out of fear that the crippling and sometimes fatal disease could not be tamed.

Before the HeLa cell line became available, testing of polio vaccine would have required killing millions of monkeys, according to Skloot. That was due to the fact that Salk's research team needed minced monkey kidney tissue to run the tests

Other breakthroughs sustained by the HeLa cell line include in vitro fertilization trials, and new anti-cancer undergoing small clinical trails today.

During an interview and in taking questions from the Westport audience, Skloot touched on the issue of doctors taking specimens from patients without their permission. She also raised ethics questions involved in firms making money off the HeLa cell line when Lacks was not paid a dime.

Skloot noted that when the book went to press, a nonprofit organization was selling HeLa cell line for $265 a vial. She also found a firm that sells various HeLa products at prices ranging from $100 to $10,000.

Skloot said when she tells people about the saga of Henrietta Lacks, the first question is: Wasn't it illegal for doctors to take Henrietta's cells without her knowledge? Don't doctors have to tell you when they use your cells in research? Her answer:

"The answer is `no'-- not in 1951 and not in 2009 when the book went to press," Skloot said. "Today most American have their tissue on file somewhere. When you go to the doctor for a routine blood test or to have a mole removed, when you have an appendectomy, tonsillectomy, or any other kind of ectomy, the stuff you leave behind doesn't always get thrown out."

Doctors, hospitals, laboratories can keep it indefinitely, she said.

About 10 years ago the Rand Corporation put out a report (the first and last its kind) with a conservative estimate that more than 307 million tissue samples from 178 million people were stored in the United States alone. They said a conservative estimate indicates that this number was increasing by more than 20 million samples each year.

The stuff sits in lab freezers, on shelves or in vats of liquid nitrogen. It's stored in military facilities, the FBI and the National Institutes of Health.

"They're in biotech labs and most hospitals. Biobanks store appendixes, ovaries, testicles, fat, even foreskin from most circumcisions," Skloot said. "They also house blood samples from most infants born in the United States since the late '60s when states started mandating screening of all newborns for genetic diseases."

Skloot said scientists use these samples to develop everything from flu vaccines to penis-enlargement products.

"Without these tissues, we would have no tests for diseases like hepatitis and HIV, no vaccines for rabies, smallpox, measles and none of the promising new drugs for leukemia, breast cancer, colon cancer and -- developers of products that rely on human biological materials would be out billions of dollars."