The long bones of your legs are not made of stone, solid and permanent. They are dynamic structures, constantly being reformed and strengthened in response to the stresses to which you subject them. Biologist George Johnson explains why understanding that is important in learning to run safely. (Photo from Sxc.hu)

Richard Sayre has wanted to be a scientist ever since his early days when he blew up a kitchen oven. Today, his scientific experiments are a little less explosive -- but more urgent. As  director of the Enterprise Rent-A-Car Institute for Renewable Fuels at the Danforth Plant Science Center, he's researching biofuels and renewable energy, specifically the possibilities of getting oil from plant algae.

Do mammals have the ability to perceive magnetic fields? A German researcher started with mole rats and learned a lot from grazing cattle and red deer. Biologist George Johnson looks at study and explains how the orientation could work.

Canada has banned the use of BPA in baby bottles, but restrictions on bisphenol A may need to go a lot further. According to biologist George Johnson, "Endocrine disruptors are man-made chemicals that mimic hormones. By sheer chance, their molecules are perfectly shaped to fit particular hormone receptors. In this case, the culprit would be a chemical mimic of estrogen that promotes cancerous growth in breast cells.

"Front and center, the obvious candidate is bisphenol A (BPA), because the molecule looks a lot like estrogen ... and because BPA is a chemical to which all of us are exposed daily."

What if animals came with bar codes? Biologist George Johnson say they come with something just as good, meaning that telling tilapia from tuna may soon be within the power of everyman. (Photo from Sxc.hu)

Up to three centuries ago, at the time of Galileo, there was no clock worthy of the name. The most technically sophisticated instruments used to measure time were sundials.

Sundials date back to about 1500 BC. And today, most are out of sight and out of mind.

Performance-enhancing drugs such as anabolic steriods must be banned: Athletes who use them are cheating and harming the body in several ways. Biologist George Johnson explains how they work and why athletes think they can beat the testing regimes. 

You're driving down I-44 about an hour south of St. Louis. You glance at another dead opossum by the side of the road.

Look again. These days, that possum is very likely to be an armadillo. (Photo from www.birdphotos.com)

As biology professor George Johnson prepares to try out for a production of War of the Worlds, his thought soar to toward those other worlds and the possibility of life on other planets.

The good news is that the AIDS epidemic has peaked. The bad news is that we have had very little luck in developing an effective AIDS vaccine. Many promising approaches have been tried, but none has worked.