White blood cells patrol the streets.

White blood cells patrol your city's streets for viral threats? Actually, those are Israeli street artists.

Uriel Sinai/Getty Images

Make no mistake: The human body is a war zone. What's more, it's a modern one, fought not on some away-game battlefield but right inside the war-torn city we call the human body.

Sure, our body's defensive forces do their part to keep the bulk of invaders out, but the enemy breached our gates a long time ago. So the struggle for health wages on inside us, amid delicate systems and crucial organs. The soldiers of our immune system fight viral spies, cancerous saboteurs, bacterial terrorists and parasitic war machines.

Modern science allows for a good bit of outside interference. Like a Cold War superpower propping up an embattled regime, we ship in our pharmaceutical weapons, high-tech surveillance equipment and the occasional blast of radioactive power.

Yet these superweapons are often far from clinical in their application.

Drop a bomb on a city block and you might wipe out enemy insurgents, but you'll also kill innocent civilians and decimate important infrastructure. You damage the very thing you aim to protect.

In the body, the situation is often the same. For example, we want to save the body from the ravages of cancer, but chemotherapy and radiation treatments damage the healthy cells, as well as the cancerous ones. What we need is something capable of making deadly accurate strikes at a cellular level -- a military drone to patrol our inner space.