Atoms, unlike bits, are hard to manipulate. Advances in how we rearrange them come slowly, but the payoff can be enormous. Think new, never-before-seen products, mass-produced from materials that once seemed exotic.

Is the quest for clean doing more harm than good? That’s the question at the heart of a debate between cleaning products makers, researchers and environmental advocates.

Peanut M&M dispensers stand in the waiting room of the New England Food Allergy Treatment Center. The children coming to the center are openly flouting rules drilled into their heads for most of their lives, avoid peanuts and potentially contaminated products at all costs.

Much more is highlighted in A Look Ahead.