Miniature lungs, breasts and other organs are being grown in dishes so scientists can study how they form, why they succumb to disease and how toxins, drugs and poisons affect them. Organ models like these are rapidly replacing animals for many lab experiments. But are the days of the petri dish also numbered, as computer models, like the virtual physiological human, become more powerful. We talk to scientists using and developing all three. Plus, a new coating stops joint replacements loosening, magnetic therapy for strokes, and plants do long division...