Pembrolizumab
Does an anticancer drug have to attack the cancer cell itself? Pembrolizumab helped change the answer by targeting a molecular "brake" that tumors can use to suppress the immune response.
Iron oxide
Humans were working with iron oxide chemistry long before chemistry had a name. Some evidence of deliberate ochre processing goes back about 100,000 years.
Barium chloride dihydrate
What did ordinary barium chloride have to do with Marie Curie's isolation of radium? The answer is a beautiful lesson in how tiny chemical differences become powerful when repeated.