The Human Body: A Cellular Cosmos to Discover

10 July 2023
10 July 2023 Christophe Martin

The human body is like a galaxy a hundred times more star-filled than the Milky Way. Indeed, our body is composed of about 37.2 trillion cells. Against 400 billion stars for the Milky Way. Excuse the understatement. Each cell is a twinkling star with its own story to tell.

Have you ever thought about the incredible diversity of cells that work together to make you, who you are?

One of the most exciting and bewildering challenges of our time is to create a complete atlas of this cellular cosmos. Why is it a puzzle? And why is it so fascinating?

Let’s embark for a moment on this interstellar journey and see why.

Imagine that you are an explorer to infinity (or almost), and beyond. And that each type of cell is a new world to discover. There are about 200 different types of cells, and each is divided into subtypes of cells, like countries with their own cultures and languages. It’s a breathtaking diversity to map, and it’s just the beginning of the story.

As if all this was not complicated enough, there is the question of time. Cells are not static. Like stars, they are born, they live, they die. From the fertilized egg, mother cells give birth to daughter cells which in turn disappear from the radars after having engendered even more daughter cells, etc. It’s a constant cycle of life, a ballet of birth and death at the cellular level. A complete cellular atlas must take into account this temporal dimension, generations and generations of cells that succeed each other and differentiate. This adds another layer of complexity to this challenge.

Then there is the question of technology. It’s like trying to navigate the cosmos with an old map and a compass. The tools we have are useful, but they have their limits. We need new technologies, new “GPS” to help us navigate this cellular cosmos.

There are several major initiatives in the world that aim to map human cells. One of the best known is the Human Cell Atlas (HCA) project, ( which is an international collaboration between thousands of scientists from various disciplines. The goal of the HCA is to create comprehensive references of all human cells as a basis for understanding human health and for diagnosing, monitoring, and treating diseases.

In addition to the HCA, there are also more specific projects that focus on certain types of cells or particular organs. For example, the BRAIN project (Brain Research through Advancing Innovative Neurotechnologies) in the United States aims to map the human brain, and the Human Protein Atlas project in Sweden aims to map the distribution of proteins in the human body.

There are also numerous individual laboratories in universities and research institutes around the world that contribute to this effort. These laboratories use a variety of techniques, including microscopy, flow cytometry, single-cell RNA sequencing, and other technologies to study human cells at an unprecedented level of detail.

But despite all these challenges, this vastness to discover, these mysteries to elucidate, imagine what we could learn. A complete cellular atlas could revolutionize our understanding of human biology as well as all diseases.

Christophe Martin