She suited up. The laminar flow hood hummed as she sprayed down the vacuum flask and a box of sterile tips. The precious flask of cells sat in the incubator, its media a perfect shade of pink. She calculated the timeline: 30 seconds to remove the old media, 45 seconds to wash twice with warm PBS, 60 seconds to add the trypsin substitute, 90 seconds to knock the cells loose, and then—the critical window—2 minutes to pellet them, remove every last trace of the trypsin inhibitor (which contained serum), and resuspend them in the exact pre-warmed, pre-mixed serum-free medium.

She called it the "Serum-Free Sprint."

Her hands moved like a concert pianist's. Aspirate. Wash. Aspirate. Wash. The PBS was a gentle waterfall against the flask wall. She could feel the clock ticking in her pulse. The cells, under the microscope, were tiny stars—fragile, non-renewable, priceless.