Albrecht Kossel: The Building Blocks of Life (1910)

Imagine for a moment that you are a detective facing the greatest mystery in history: What are we actually made of? At the end of the 19th century, science thought it had the answer. Scientists were convinced that proteins were the queens of biology. They thought these gigantic, complex molecules were responsible for transmitting inheritance, moving muscles, and keeping our secrets. However, in a corner of a German laboratory, a man named Albrecht Kossel suspected we were looking at the wrong puzzle.

Kossel was not a man of grand gestures or heroic speeches. He was a meticulous chemist, a seeker of small pieces. While everyone else focused on proteins, he decided to dive into a sticky, strange substance found in the nucleus of cells, something they called 'nuclein' back then. For most, nuclein was simply scaffolding, an unimportant support material, much like the cardboard of a shoebox that you throw away once you take out the new sneakers.

But Kossel had a hunch. If the cell nucleus was the command center of life, what was inside couldn't be trash. With infinite patience, he began to 'cook' that substance, breaking it down using acids and heat, trying to see if there was something else hidden inside. What he found were not more proteins, but something no one expected: a series of chemical fragments that repeated over and over again. They were pieces of a puzzle no one knew existed.

• He searched in salmon sperm.
• He searched in thymus gland cells.
• He searched in brewer's yeast.

In all those places, no matter how different the species were, Kossel found the same components. It was as if he had discovered that all the books in the world, from a romance novel to an instruction manual, were written with the same letters. But how could simple chemical molecules contain the instructions to build a complete human being? And how is it possible that we ignored the true alphabet of existence for so long?