Subtitles section Play video Print subtitles Hi this is David from MinuteEarth. And these are my fingerprints. Each one has a particular pattern on it: a whorl, a loop, an arch, or in the case of my left thumb, a somewhat rarer double loop whorl. But even if your left thumbprint has one of the boring patterns, your print is unique to you. In fact, there's no one in the world - past, present, or future - who has a fingerprint that matches any one of yours. To understand why, we first need to know how they form. Early on in fetal development, lumps of stem cell tissues - called volar pads - grow under the skin on each finger. Whether the volar pad is small or big or off to the side or grows unevenly determines the main pattern of the fingerprint - an arch, whorl, loop, or even a very interesting and exciting double loop whorl. Because your volar pad size and orientation is somewhat genetic, many relatives, and most identical twins, have the same main patterns on each finger, and so DNA alone isn't where the uniqueness of fingerprints comes from. Instead, it comes from the chaotic way in which the fingerprints grow. On top of the volar pads, the embryonic skin has several layers of cells, all growing at different rates. And as the inner layer grows, the middle layer buckles, causing ridges to form in the upper layer. The ridges first form parallel to the three areas of greatest stress on a growing finger: near the fingernail, near the crease at the first joint, and on top of the volar pads. As the ridge lines grow, they sometimes run into one another, resulting in either a block or a split. The details of precisely where on the finger those ridge lines meet up and whether each one get turned into a dead end or a fork is determined by a bunch of different factors, like how nerves and capillaries grow in the layer below the skin, fluid pressure changes in the womb, and even which direction the finger is oriented relative to gravity. And because there are chaotic and unpredictable differences in each of these, whether a given ridge becomes a dead-end or a fork is essentially random, even for babies that develop in the same womb. The average person has around 50 forks or dead ends at different places on each fingerprint. Even if you oversimplify things - ignoring position and so on - and just think of each of these points as an independent coinflip between fork and dead end, there are more than a quadrillion different possibilities for fingerprints. To get a sense of how many possibilities that is, there are 80 billion fingerprints in the world, which are represented by this black dot. A quadrillion is 10,000 times larger. And, remember, this is a simplification, because the number of potential unique fingerprints gets way, way bigger when you take into account the relative positions of these points. So my left thumbprint - and all my fingerprints and all your fingerprints - are each pretty much mathematically guaranteed to be unique - to be the only ones in the whorl. Each of your fingerprints is one of a kind, and each of your passwords should be, too. That's why I use Dashlane, who sponsored this video. Dashlane randomly generates a unique strong password whenever I sign up for a new account, and instantly logs me back in whenever I return to the site. It also securely autofills my personal information whenever I need to fill out online forms and lets me know if there's been a data breach at any of my regular haunts. The basic service is free, but with Dashlane Premium I can access Dashlane on all my devices and store unlimited passwords. And you know the best part? I can use my own unique fingerprint to open my Dashlane password vault on my phone! To download your own free 30-day trial of Dashlane Premium, go to Dashlane.com/MinuteEarth. The first 200 viewers can also get 10% off a yearly Dashlane Premium membership using the code MINUTEEARTH at checkout.