Explain SMBC — the wiki for Saturday Morning Breakfast Cereal

This comic shows a "Science Toys" store where a child receives a "Stem Cell Creation Kit." The child excitedly opens the kit and throws something at another child while yelling "Stem cell!" -- apparently treating stem cells like a weapon or projectile. The final panel shows what appears to be actual stem cell research equipment (a flask and a petri dish) sitting unused.

The humor lies in the gap between the lofty promise of a science toy meant to educate children about cutting-edge biology, and the reality of how children actually play -- by turning everything into a projectile. It also pokes fun at the idea of marketing complex biotechnology as a children's toy, since real stem cell research requires sophisticated laboratory equipment and training, not a toy kit.