All things are made of atoms, little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another.

Rich Feynman

Humans—of all ages and cultures—are confronted with the same question: the question of how to overcome separateness, to achieve union, to transcend one’s own individual life and find at-onement.

Erich Fromm, Art Of Loving

We sense and define the borders of ourselves with skin: boundary, sentry, pigment, signal. Skin is where we are vulnerable, where our heat is lost, and where we must make contact to live and mate. Skin plays many roles, and so bears its own diversities and contradictions.

On our soft ventral sides, along the midline from throat to abdomen to pelvis—the front of a human being, derived from the ground-facing aspect of a four-legged reptile or early mammal—blood flows toward the surface for blushing and swelling, to reach out, to functionalize, to couple.

Our hair-raising, tingling, rageful, boundary-violated feeling is instead felt and expressed dorsally, along the back—the more secret, less visible side of human beings, paradoxically facing away from the individual confronting us. But in our evolutionary history before standing upright, this was the more noticeable upper side, where like the ruffs and backs of cats and wolves, hairs could rise to help us expand our presence.

Karl Deisseroth, Projections

If we could see more than meets the eye, we could watch as a clump of cells grows into a human being in a woman’s belly. We would suddenly see how we develop, roughly speaking, from three tubes.

The first tube runs right the way through us, with a knot in the middle. This is our cardiovascular system, and the central knot is what develops into our heart.

The second tube develops more or less parallel to the first along our back. Then it forms a bubble that migrates to the top end of our body, where it stays put. This tube is our nervous system, with the spinal cord, including the brain, at the top and myriad nerves branching out into every part of our body.

The third tube runs through us from end to end. This is our intestinal tube—the gut. The intestinal tube provides many of the furnishings of our interior, including our lungs, liver, and pancreas. It is involved in the complex construction of our mouth, creates our esophagus, with its ability to move like a break dancer, and develops a little stomach pouch so we can store food for a couple of hours. And, last but not least, the intestinal tube completes its masterpiece—the eponymous intestine or gut.

Guilia Enders, Gut