One of these things is not like the other: A 3-D printed model of a beige cowbird egg stands out from its robin's egg nest mates, though their shape and heft are similar. Ana Lopez/Courtesy of Mark Hauber hide caption

itoggle caption Ana Lopez/Courtesy of Mark Hauber

This fungus among us — baker's yeast, aka Saccharomyces cerevisiae — is useful for more than just making bread. iStockphoto hide caption

itoggle caption iStockphoto

The most recent common ancestor of all today's snakes likely lived 120 million years ago. Scientists believe it used needle-like hooked teeth to grab rodent-like creatures that it then swallowed whole. Julius Csotonyi/BMC Evolutionary Biology hide caption

itoggle caption Julius Csotonyi/BMC Evolutionary Biology

The skull of a chicken embryo (left) has a recognizable beak. But when scientists block the expression of two particular genes, the embryo develops a rounded "snout" (center) that looks something like an alligator's skull (right). Bhart-Anjan S. Bhullar hide caption

itoggle caption Bhart-Anjan S. Bhullar

ADP Co-chairs Daniel Reifsnyder (left) and Ahmed Djoghlaf (center) say their negotiation work is difficult but worth it. "We only have one planet, you know," Reifsnyder says. "We have to protect it." Courtesy of IISD/ENB hide caption

itoggle caption Courtesy of IISD/ENB

Loki's Castle, the field of deep sea vents between Norway and Greenland, is home to sediments containing DNA from the newly discovered archaea. R.B. Pedersen/Centre for Geobiology, Bergen, Norway hide caption

itoggle caption R.B. Pedersen/Centre for Geobiology, Bergen, Norway

Humans have influenced Earth's history for thousands of years, though some scientists count changes of the last two centuries as especially notable. (Left to right) Universal History Archive/UIG via Getty Images; Hulton Archive/Getty Images; Liszt Collection/Heritage Images/Getty Images; Joint Task Force One/AP hide caption

itoggle caption (Left to right) Universal History Archive/UIG via Getty Images; Hulton Archive/Getty Images; Liszt Collection/Heritage Images/Getty Images; Joint Task Force One/AP

NASA astronaut Scott Kelly is seen inside a Soyuz simulator at the Gagarin Cosmonaut Training Center on March 4 in Star City, Russia. Kelly, along with Russian cosmonaut Mikhail Kornienko of the Russian Federal Space Agency, are scheduled for launch Friday aboard a Soyuz TMA-16M spacecraft from the Baikonur Cosmodrome in Kazakhstan. NASA/Bill Ingalls hide caption

itoggle caption NASA/Bill Ingalls

Water molecules between two layers of graphene arranged themselves in a lattice of squares — unlike any other known form of ice. NPG Press via YouTube hide caption

itoggle caption NPG Press via YouTube

N. gardneri mushrooms grow at the base of young babassu palms in Brazil. A bland tan by day, the fungi emit an eerie green light by night. Michele P. Verderane/IP-USP hide caption

itoggle caption Michele P. Verderane/IP-USP

Mars, anyone? Six researchers from the Mars Society sport their best space duds during this 2014 simulation of the conditions that explorers of the Red Planet might face. (From left) Ian Silversides, Anastasiya Stepanova, Alexandre Mangeot and Claude-Michel Laroche. Micke Sebastien/Paris Match via Getty Images hide caption

itoggle caption Micke Sebastien/Paris Match via Getty Images

The size of the brain of a chimpanzee (right) is considerably smaller than that of a human brain. Probably multiple stretches of DNA help determine that, geneticists say. Science Photo Library/Corbis hide caption

itoggle caption Science Photo Library/Corbis

The eruption of Mount Pinatubo in the Philippines in 1991 spewed almost 20 million tons of sulfur dioxide into the atmosphere, causing worldwide temperatures to drop half a degree on average. Arlan Naeg/AFP/Getty Images hide caption

itoggle caption Arlan Naeg/AFP/Getty Images

Stars over the Cerro Tololo Inter-American Observatory in Chile. Sheppard and Trujillo used the new Dark Energy Camera (DECam) on a telescope there to find the distant dwarf planet 2012 VP 113. Reidar Hahn/Fermilab hide caption

itoggle caption Reidar Hahn/Fermilab