It StARtS It cell splits to become ter just forty-seven doublings, you en trillion(10,000,000,000,000,000) cells in your body and are ready to spring forth as a human being.

    1And every one of tly o do to preserve and nurture you from t of conception to your last breath.

    You s from your cells. t you te genetic code—truction manual for your body—so itkno only o do its job but every oto remind a cell to keep an eye on its adenosine tripe levels or to find a place fortra squirt of folic acid t’s just unexpectedly turned up. It  for you, andmillions more things besides.

    Every cell in nature is a t are far beyond ts ofy. to build t basic yeast cell, for example, you urize about ts as are found in a Boeing 777 jetliner andfit to a sp five microns across; to persuade tspo reproduce.

    But yeast cells are as not just more variedand complicated, but vastly more fascinating because of teractions.

    Your cells are a country of ten trillion citizens, eaced in some intensivelyspecific o your overall  a t do for you. tyou feel pleasure and form ts. to stand and stretc, tract trients, distribute tes—all t in junior  to make you place and reer you forget to eat again. tlypurring. to your defense tantyou are tened. tatingly die for you—billions of t once in all your years  us take a moment nooregard tion they deserve.

    e understand a little of  ormanufacture insulin or engage in many of ts necessary to maintain a complicatedentity like yourself—but only a little. You  least 200,000 different types of protein1Actually, quite a lot of cells are lost in t, so t a guess. Depending on ude. ten trillion (or quadrillion) is from Margulis and Sagan, 1986.

    laboring aand  2 percent oft t more like 50 percent; it depends, apparently, on and.”)Surprises at turn up all time. In nature, nitric oxide is a formidabletoxin and a common component of air pollution. So scientists urally a little surpriseded manner ins purpose  first a mystery, but tists began to find it all over trolling ttacking cancers andoting ting in penile erections. It alsoexplained  pain kno is converted into nitric oxide in tream, relaxing to floance  from extraneous toxin to ubiquitous elixir.

    You  possess  “some  feypes of cell, according to t Cian de Duve, and ts can stretco several feet to tiny, disc-so tocells t o give us vision. tuously  t of conception, s an egg eigimes bigger t (ionof male conquest into perspective). On average,  tymicrons  is about to be seenbut roomy enougo ed structures like mitoc literal ’s a someion to reflect t every inc you are lugging around about five pounds of deadskin, of s are slougy stern very largely in old skin.

    Most living cells seldom last more t tableexceptions. Liver cells can survive for years, ts  as long as you do. You are issued a  birt is all you are ever going to get. It imated t you lose fiveo do t a momentto e. t ts of your brain cells are constantlyrene, as  of tually likely to be more ta mont ed t t a single bit of any of us—not somucray molecule—t  of us nine years ago. It may not feel like it, but at ters.

    t person to describe a cell   encounteredsquabbling on over credit for tion of ty-eigician anda dab  making ingenious and useful instruments—but not er admiration tions ofMiniature Bodies Made by Magnifying Glasses, produced in 1665. It revealed to an encedpublic a universe of t ructuredto imagining.

    Among tures first identified by tle cst ed t aone-incain 1,259,712,000 of tiny cappearance of sucime ion or so, but   ecions of ty times, making t eentury optical technology.

    So it came as somet a decade later y began to receive dras from an unlettered linendraper in ions of up to 275 times. toni van Leeule formal education and no background inscience, ive and dedicated observer and a technical genius.

    to t is not knoions from simpletle more t iny bubble ofglass embedded in t most of us t really not mucrument for everyexperiment remely secretive about ecimes offer tips to tis improve tions.

    2Over a period of fifty years—beginning, remarkably enougforty— to ty, all ten in Locongue of ations, but simplyts of s on almosteveryt could be usefully examined—bread mold, a bee’s stinger, blood cells, teet, and semen (t ful apologies for ture)—nearly all of which had never been seen microscopically before.

    After ed finding “animalcules” in a sample of pepper er in 1676, ty spent a year  devices Englisectle animals” before finally getting tion rigLeeu tinybeings in a single drop of er—more teemed  no one ed.

    Inspired by Leeuic findings, oto peer into microscopes  times found t  in fact tedDutcsoecker, le beings “ime many people believed t allures—ly inflated versions of tiny but completeprecursor beings. Leeuhusiasms.

    In one of  successful experiments ried to study ties ofgunpo at close range; he process.

    2Leeuable, tist Jan Vermeer. In tent but not outstanding artist, suddenly developed tery of ligive for   ed t ing images onto a flat surface ted among Vermeers personal effects after  it  tor ofVermeers estate oni van Leeuive lens-maker of his day.

    In 1683 Leeu t  as far as progress could getfor t century and a ations of microscope tec until1831  see t tisanistRobert Bro frequent but alo tory of science. Bro nucleus from tin nucula, meaning little nut or kernel.

    Not until 1839,  all living matter is cellular. It , and it  only comparatively late, as scientificinsig not  first. It  until teur in France, t it  arisespontaneously but must come from preexisting cells. t is the basis of all modern biology.

    to many t James trefil) to “a vast, teeming metropolis” (t Guy Bro is like a refinery in t it is devoted to civityon a grand scale, and like a metropolis in t it is croeractions t seem confused and random but clearly em to t it is amucmarisy or factory t you o begin y doesn’t meaningfully apply at t an atom’s ivity every  feel terribly electrical, but you are. t and to electricity. t give eac is t it is alliny scale: a mere 0.1 volts traveling distances measured in nanometers.

    up and it ranslate as a jolt of ty million volts per meter, abouttorm.

    ever t to fundamentally the same plan:

    ter casing or membrane, a nucleus ion to keep you going, and a busy space betoplasm. t, as most of us imagine it, a durable, rubbery casing, somet you is made up of a type of fatty material knoency “of a ligo quoteS seems surprisingly insubstantial, bear in mind t at tly. to anyter becomesa kind of y gel, and a lipid is like iron.

    If you could visit a cell, you  like it. Bloo a scale at  tself oskeleton. it, millions upon millionsof objects—some tballs, ot likebullets. t be a place you could stand  being pummeled and rippedtimes every second from every direction. Even for its full-time occupants trand of DNA is on average attacked or damagedonce every 8.4 seconds—ten times in a day—by cs t, and eac be sly stitc to perish.

    teins are especially lively, spinning, pulsating, and flying into eaco abillion times a second. Enzymes, type of protein, daso a tasks a second. Like greatly speeded up s, to t one. Some monitorpassing proteins and mark  are irreparably damaged or flaed, teins proceed to a structure called a proteasome, s used to build neeins. Some types of protein existfor less t all lead existences t areinconceivably frenzied. As de Duve notes, “t necessarily remainentirely beyond tion oo t.”

    But sloo a speed at ions can be observed, and t seem quite so unnerving. You can see t a cell is just millions of objects—lysosomes,endosomes, ribosomes, ligands, peroxisomes, proteins of every size and somillions of ots and performing mundane tasks: extracting energy from nutrients,assembling structures, getting rid of e, ruders, sending and receivingmessages, making repairs. typically a cell ain some 20,000 different types of protein,and of t 2,000 types  least 50,000 molecules. “t even if  only t in amounts of moretotal is still a very minimum of 100 million protein molecules in eacaggering figure gives some idea of ty of biocivity hin us.”

    It is all an immensely demanding process. Your  must pump 75 gallons of blood an’s enougo fill four Olympic-sized so keep all ted. (And t’s at rest. Duringexercise te can increase as mucaken up by tocations, and t a typical cell, t a cell does and  requires.

    You may recall from an earlier cer t toc to edas captive bacteria and t tially as lodgers in our cells, preserving tic instructions, dividing to timetable, speaking t  tually all take into your body are delivered, after processing, to toced into a molecule called adenosine tripe, or AtP.

    You may not P, but it is P molecules areessentially little battery packs t move t t of it. At any given moment, a typical cell in your bodyP molecules in it, and in tes every one of taken tP equivalent to about . Feel t’s your AtP at work.

    can only be called great dignity. take doruts and buttresses t ogetly devour t parts. tosis or programmed cell deat and billions of otly—for instance,  mostly told to.

    Indeed, if not told to live—if not given some kind of active instruction from anotomatically kill t of reassurance.

    o expire in t rato divide and proliferate  cancer. Cancer cells are really justconfused cells. Cells make take fairly regularly, but temec. It is only very rarely t t of control. Onaverage, al malignancy for each 100 million billion cell divisions.

    Cancer is bad luck in every possible sense of term.

    t t t t t a stretcantly sending andmonitoring streams of messages—a cacophe body:

    instructions, queries, corrections, requests for assistance, updates, notices to divide or expire.

    Most of tities sucrogen, and testosterone t convey information from remote outpostslike till otelegrapers in a process called paracrine signaling. Finally, cells communicatedirectly o make sure tions are coordinated.

    is per remarkable is t it is all just random frantic action, a sequence ofendless encounters directed by notal rules of attraction and repulsion.

    tions of t all just edly and so reliably t seldom are , yet some just order  a perfect  across the organism.

    In  and, trillions upon trillions of reflexive cions add up to a mobile, to t, a rative but still incredibly organized dung beetle. Every living t, is aomic engineering.

    Indeed, some organisms t ive enjoy a level of cellular organizationt makes our orian. Disassemble tance), to a solution, and togeto a sponge again. You can do to to continue to be.

    And t’s because of a curious, determined, barely understood molecule t is itself notalive and for t part doesn’t do anyt all. e call it DNA, and to begin tounderstand its supreme importance to science and to us o go back 160 years or so toVictorian England and to t  C  idea t anyone  take a littleexplaining, locked it a fifteen years.