We measure our lives in months and years. The wood mouse’s life is measured in hours and days. This tiny mammal, a member of the rodent family, has a childhood lasting only for three weeks.

Survival is a difficult task for such a small creature. The wood mouse ventures out mainly at night, using its whiskers to feel its way through the darkness. It has good sight and hearing, and an excellent sense of smell. However, the wood mouse is relatively defenseless, and many fall prey to owls, hawks, crows, foxes, and other predators.

The mouse’s main survival strategy is to breed at speed. A single mother may have several litters of babies, totally 25 to 30 offspring in a year. With so many babies, the chances are that only one or two will survive.

The wood mouse has many similarities to its close cousin, the house mouse. For both, life starts in a cozy nest. The new babies are pink and furless. Their eyes are closed, and there is no sign of the typically large mouse ears. They depend completely on their mother. She suckles them with her milk, licks them clean, removes their droppings, and keeps the nest clean. If they wriggle too far, she picks them up in her mouth and returns them to the nest.

      In the first century A.D. Pompeii was a pretty and prosperous resort town. There were some 12,000year-round inhabitants and hundreds more who came down from Rome each summer to their villas by the sea. Ona hot summer day, around noon—it was August 24, A.D. 79—the people of Pompeii saw a huge cloud formingover the mountain north of the city. This was the last noontime Pompeii would ever know, because that cloud ofvolcanic debris was the beginning of a massive eruption that blew the top off Vesuvius, burying the city beneath 12 feet of rock and ash and unleashing a blast of toxic gases. Thousands were killed—in their homes, in thestreets, in businesses and brothels. Thousands more fled madly toward the sea. Those who were running for theirlives must have been surprised to see a curious figure racing not from but toward the volcano. This was the greatRoman naturalist Pliny the Elder. Seeing the initial eruption from a safe distance at his home near Naples, therenowned scientific observer just could not stay away. He grabbed his notebook and stylus and hightailed it forPompeii to gather firsthand information on this prodigious phenomenon. Pliny’s curiosity cost him his life.