A recent study found a brief delay in peak growth spurt among boys who took ADHD stimulants for at least three years, but no significant effect on their ultimate height. iStockphoto hide caption

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Researchers raised two groups of walking, air-breathing Polypterus senegalus — one on land and one on the water. They discovered that each group was able to adapt to be best suited to its environment. A. Morin, E.M. Standen, T.Y. Du, H. Larsson/McGill University hide caption

itoggle caption A. Morin, E.M. Standen, T.Y. Du, H. Larsson/McGill University

A technician tests samples from Ebola-infected patients at a field lab, run by Doctors Without Borders, in Kailahun, Sierra Leone. Tommy Trenchard for NPR hide caption

itoggle caption Tommy Trenchard for NPR

The granulated surface of the lake bed known as the Racetrack is a favorite destination for tourists — and for scientists who want to investigate trails left by the meandering stones. Momatiuk - Eastcott/Corbis hide caption

itoggle caption Momatiuk - Eastcott/Corbis

A scientist tests a patient's blood for Ebola at the European Mobile Laboratory in Gueckedou, Guinea. The first cases reported in the outbreak occurred in a small village about eight miles outside Gueckedou. Misha Hussain /Reuters /Landov hide caption

itoggle caption Misha Hussain /Reuters /Landov

Marqui Ducarme is aided by his wife after catching chikungunya at his home in Port-au-Prince, May 23. The virus swept through Haiti this spring, infecting more than 40,000 people. Marie Arago/Reuters/Landov hide caption

itoggle caption Marie Arago/Reuters/Landov