"Liver buds" grow in petri dishes. The rudimentary organs are about 5 mm wide, or half the height of a classic Lego block. Courtesy of Takanori Takebe/Yokohama City University Graduate School of Medicine hide caption

itoggle caption Courtesy of Takanori Takebe/Yokohama City University Graduate School of Medicine

Chimpanzee Toni celebrated his 50th birthday at the Hellabrunn Zoo in Munich on Nov. 22, 2011. Sven Hoppe/DPA/Landov hide caption

itoggle caption Sven Hoppe/DPA/Landov

This model of a molar shows color-coded barium banding patterns that reveal weaning age. Ian Harrowell, Christine Austin, Manish Arora/Harvard School of Public Health hide caption

itoggle caption Ian Harrowell, Christine Austin, Manish Arora/Harvard School of Public Health

Fungi (cyan) surround a human hair within the skin. A study in the journal Nature shows the population of fungi on human skin is more diverse that previously thought. Alex Valm, Ph.D. hide caption

itoggle caption Alex Valm, Ph.D.

Nanoflowers, each smaller than the thickness of a dollar bill, sprout up spontaneously on a surface dipped in salts and silicon. Courtesy of Wim Noorduin/Harvard University hide caption

itoggle caption Courtesy of Wim Noorduin/Harvard University

After President Obama overturned Bush-era policy restricting federal funding of embryonic stem cell research in 2009, Nebraska Right to Life led a protest of the research outside the University of Nebraska regents' meeting. Nati Harnik/AP hide caption

itoggle caption Nati Harnik/AP

Human embryos grow in a petri dish two days after scientists in Oregon cloned them from a donor's skin cell. http://www.flickr.com/photos/ohsunews/8726915230/in/photostream//Courtesy of OHSU Photos hide caption

itoggle caption http://www.flickr.com/photos/ohsunews/8726915230/in/photostream//Courtesy of OHSU Photos

A scientist removes the nucleus from a human egg using a pipette. This is the first step to making personalized embryonic stem cells. Courtesy of OHSU Photos hide caption

itoggle caption Courtesy of OHSU Photos