An organelle called the nucleolus resides deep within the cell nucleus and performs one of the cell's most critical functions: it manufactures ribosomes, the molecular machines that convert the genetic information carried by messenger RNA into proteins that do the work of life.

Living things are resourceful, which is a comforting thought unless the living thing in question is a pathogen or a cancer cell. Noxious cells excel at developing drug resistance, outwitting immune systems, and evading cellular controls. They even show an unhealthy talent for surviving internal perturbations such as mutations that affect the function of vital genes, and they do this by evolving new mechanisms to perform old tasks. Somehow the bad guys find a workaround.

Most people have heard that human inheritance is spelled out in our DNA and activated through our genes. Yet few know anything about epigenetics, a variety of methods that our cells have evolved to transmit heritable changes without changing DNA.

How the chicken got its feathers in the right place is not a Rudyard Kipling “Just So” story, but an illustration of how simple causes can stack up into complicated results. For a chicken, it’s the difference between having feathers arranged in spots or stripes. For biologists at the University of Southern California and mathematicians at Oxford University in the UK, it’s all a question of patterning.