That was it. That was the whole secret.

It was the smell that hit Jamie first. Not the sterile, clinical scent of a hospital, but the sweet, cloying perfume of the biology lab: preservative, agar, and the faint ghost of a dissected frog from third period.

Jamie’s eyes widened. That was the gradient. The concentration was higher outside. The molecule wanted to stay out. But the cell needed it in.

Then the weird thing happened. The room didn't change, but Jamie’s attention did. It was like those magic-eye posters from the dentist’s office—if you stared long enough, the hidden shape popped into focus.

How?

Jamie sat bolt upright.

Jamie hated this room. More specifically, Jamie hated the giant, sagittal-cut model of the human cell that loomed in the corner, its cross-section painted in garish primary colors. Today, Ms. Albright was scrawling a diagram on the whiteboard: a lopsided circle with a yellow dot in the middle.