DNA (Deoxyribonucleic acid)

What am I. I am a secret recipe book hiding inside every living thing, from the tallest trees to the smallest ladybugs, and even inside of you. I decide if a kitten will have striped fur or if a flower will have pink petals. For you, I decide the color of your eyes, whether your hair is curly or straight, and even how tall you will grow. Imagine a super long, twisty ladder, but so tiny it can be coiled up tightly inside every one of your cells. That's me. I hold all the special instructions for building everything that makes you, you. It's my job to pass these instructions on. Hello. I am DNA, which is short for my very long name: Deoxyribonucleic acid. It’s nice to finally introduce myself.

For a very long time, I was a huge puzzle that scientists all over the world wanted to solve. They knew I existed deep inside of cells, but they didn't know what I looked like or what my important job was. A scientist named Friedrich Miescher was the very first person to find me way, way back in 1869 while he was studying cells under his microscope. He saw me, a mysterious substance, but he had no idea I was the amazing instruction book for all of life. So my secrets remained hidden for many more years. Then, in the early 1950s, a brilliant and careful scientist named Rosalind Franklin got much closer to solving the puzzle. She used a special X-ray machine to take a picture of me. It was like taking a picture of a ghost. The photograph was the first time anyone had seen my beautiful, crisscrossing, spiral shape. Her picture was like a secret treasure map. Two other scientists, James Watson and Francis Crick, saw her amazing picture, and it was the final clue they needed to put all the pieces together. It helped them understand my exact shape. On April 25th, 1953, they built a big model out of metal pieces to show everyone what I looked like. My secret was finally out. I was a 'double helix,' which is a fancy way of saying I look just like a twisting ladder.

Now that scientists finally understood my twisting ladder shape, they could start to learn how to read my instructions. Think of it like learning a new secret code. Understanding this code is one of the most important discoveries ever. It helps doctors understand why people get sick and how to invent medicines to make them better. It helps police officers solve mysteries by looking at tiny clues that people leave behind. My instructions can even tell you about your family from long, long ago, showing you where your great-great-grandparents might have lived. I am the story of you, written in a special code inside every part of your body. I connect you to your parents, your grandparents, and every living thing on Earth. I am so proud to be the special blueprint that makes you, you.