Joshua Weinstein spent hours in graduate school pulverizing zebrafish in a blender. That was a normal first step toward sequencing the fish’s genes, but it had a high “ick” factor — and he felt like it wasn’t very good science. Although his results would tell him about the fish’s overall genetic activity, they couldn’t reveal which genes were present and active in different places: like inside the fish’s immune tissue or its nerves, or within a cancerous tumor. And he wanted to know.