Georgetown's Robert Clark says it's very difficult to say precisely how many experiments have been spoiled by contaminated cell lines. Phil Humnicky/Courtesy of Georgetown University hide caption

itoggle caption Phil Humnicky/Courtesy of Georgetown University

Do you want to go to the park? Mango Doucleff, of San Francisco, responds to her favorite command by perking up her ears and tilting her head. Michaeleen Doucleff/NPR hide caption

itoggle caption Michaeleen Doucleff/NPR

A turkey vulture makes quick work of a dead rabbit at Martin Luther King Jr. Regional Shoreline park in Oakland, Calif. Sebastian Kennerknecht/Minden/Corbis hide caption

itoggle caption Sebastian Kennerknecht/Minden/Corbis

Women participate in a breast cancer fund-raising in Denver in 2011. Despite decades of awareness campaigns, the survival rate for women with metastatic breast cancer hasn't improved. Helen H. Richardson/Denver Post/AP hide caption

itoggle caption Helen H. Richardson/Denver Post/AP

Caltech biochemical engineer Frances Arnold was awarded a National Medal of Technology and Innovation by President Obama in 2013. Jason Reed/Reuters/Landov hide caption

itoggle caption Jason Reed/Reuters/Landov

Researcher Svante Pääbo, was able to extract a complete genome from this ancient human leg bone. Bence Viola/Max Planck Institute for Evolutionary Anthropology hide caption

itoggle caption Bence Viola/Max Planck Institute for Evolutionary Anthropology

Isabella Beukes, of Santa Rosa, Calif., has been legally blind for more than 40 years. An experimental treatment derived from embryonic stem cells seems to have enabled her now to see not just color but also some shapes. Tim Hussin for NPR hide caption

itoggle caption Tim Hussin for NPR

Insulin is produced by the green cells that are in clusters about the same size as the islets in the human pancreas. The red cells are producing another metabolic hormone, glucagon, that prevents low blood sugar. Harvard University hide caption

itoggle caption Harvard University

Randen Patterson left a research career in physiology at U.C. Davis when funding got too tight. He now owns a grocery store in Guinda, Calif. Max Whittaker/Prime for NPR hide caption

itoggle caption Max Whittaker/Prime for NPR

Justin McCowan, 39, has Down syndrome and lives at home with his parents in Santa Monica, Calif. Benjamin B. Morris for NPR hide caption

itoggle caption Benjamin B. Morris for NPR

Houston Texans Coach Bill O'Brien (center) Chief Operating Officer Cal McNair (right) and Houston Chronicle reporter Brian Smith take the ALS Ice Bucket Challenge Thursday to raise money for the ALS Association. David J. Phillip/AP hide caption

itoggle caption David J. Phillip/AP

Clear and clean, bubble wrap is well-suited to serve as an array of tiny test tubes. Here a dye solution is injected into the bubbles to measure the hemoglobin concentration in blood. American Chemical Society hide caption

itoggle caption American Chemical Society

The heart beats in a mouse embryo grown with stem cells made from blood. Now the research that claimed a simple acid solution could be used to create those cells has been retracted. Courtesy of Haruko Obokata hide caption

itoggle caption Courtesy of Haruko Obokata