print-2
Explanation
This comic connects three real scientific/engineering facts and then draws an absurd (but technically logical) conclusion from their combination.
The first panel introduces "goo printers" -- 3D printers that use thermopolymers, materials that solidify into specific shapes when heat is applied in controlled patterns. The second panel explains thermal coagulation, the real biological process by which blood irreversibly solidifies when heated to a sufficient temperature. The third panel describes ultrasonic heating, a real technology that can deliver focused energy to precise locations inside fluids (used in medical applications like HIFU -- High-Intensity Focused Ultrasound).
The punchline comes from combining all three facts into a single horrifying application: if you can shape materials with targeted heat, and blood solidifies with heat, and you can deliver heat to precise locations inside a fluid (like a person's bloodstream), then a state actor could theoretically assassinate someone by forming shaped blood clots inside their body -- essentially "3D printing" a national symbol inside their victim's circulatory system. The final panel depicts investigators discovering that a victim's blood vessels are filled with clots shaped like the Canadian maple leaf, revealing who carried out the assassination.
The humor lies in the classic SMBC pattern of taking legitimate scientific premises and following them to a logical but deeply disturbing and darkly comedic conclusion. Canada is chosen as the assassinating country for additional comedic effect, since Canada is stereotypically seen as polite and non-threatening, making it the last nation you'd expect to be committing high-tech assassinations. The fact that the "calling card" would be "amazing" adds a layer of absurd pride in what would be a monstrous act.