This is how you began. Follow the stages from conception to first breath through ten illustrations from cell biologist Katharina Vestre’s new book ‘The Making of You’. Illustrations by Linnea Vestre.
Your journey from cell to human
Words by Katharina Vestreartwork by Linnea Vestre
- In pictures

A sperm cell may be blind and deaf, but that doesn’t stop it making its way through a landscape it’s never even been close to before… The winner discards its tail, melts into the egg and releases its valuable cargo: 23 of the father’s chromosomes. At the same instant, the egg cell releases substances that create a hard capsule around it so that no more sperm can enter… The race is over. The making of you can begin.

It is one day after your conception, and the small hairs in the fallopian tube are nudging the tiny round cell down the canal. Slowly. Carefully. On the outside, everything looks perfectly calm. Deep within the cell’s interior, however, a sophisticated mechanism is working tirelessly, creating precise copies of your DNA molecules.

By week three you look like a little round plate. On each side of the plate are two fluid-filled sacs. One of them becomes the foetal sac… The other will become the yolk sac… The yolk sac creates your first blood cells; a job that your liver, spleen and your bone marrow will eventually take over. When it’s no longer needed, the yolk sac will shrivel up and become part of your intestines.

Week four: time we stepped back and admired you a little. You’re no longer a single disc. You’re only a few millimetres long – but you have a top and a bottom, a front and a back, and your first organs are growing inside. You also have a pulsating red heart tube, a nerve tube expanding in your head, and a bowel tube running through your furry, transparent body.

By the start of week five you are the size of a pea… Previously, everything your cells have done has seemed quite logical. But now it looks like they have messed up. Why, for example, are they building this totally unnecessary tail? It will end up being no more than a bony stump that hurts when you fall on your ass. No engineer in his right mind would do anything similar.

By the start of the third month you’re about as big as a strawberry. Your nose is wide and blunt, your eyes are far apart… During this month it will become possible for the first time to see if you are going to be male or female. For the first few weeks there are no differences between the sexes, and this is probably why boys have nipples – not because they need them, but because they are already in place before the sex differences stand out.

At the beginning of the fourth month, you are about as big as an avocado… Sometimes you might stretch your arms out slightly, or suck your thumb. (By the way, the thumb you choose to suck is no casual matter: most of us prefer the thumb on the right hand, but left-handed people often choose the left thumb before they are born.)

By the start of the fifth month you are about as long as a banana… Your ears have crept up your neck and are now in the right place. Before long, you will begin reacting to sound. Meanwhile, other senses are already working. The first to come online was your sense of touch… You will often explore your face with your hands, and put your fingers on your lips several times a day.

By the beginning of the sixth month, you resemble a newborn baby, just smaller and more fragile… It is possible to save babies born as early as in the 20th week (pregnancy week 22), but the chances of surviving such an early birth are low. At best, only about one in three make it, and many of them sustain life-lasting damage. By comparison, about 90 per cent survive if the birth occurs five weeks later.

Full term: it’s the end of your journey – and the beginning of a new one. At this point you just have to get out. If your head gets bigger, it will be impossible to squeeze out through the narrow birth canal… Access to oxygen is also quite poor in the womb… so if your brain is to keep growing, then your lungs must get enough fresh air. You simply have to get out; you have to breathe. Right now.
About the contributors
Katharina Vestre
Katharina Vestre is a cell biologist and doctoral research fellow at the University of Oslo Department of Biosciences. ‘The Making of You’ is her first book.