Molecule of the Week (MOTW)

This Week's Clue

You won’t find much of us in your supermarket’s tomatoes.

What molecules are we?


A reference and quiz in one fun app! Check out the clue, then guess what the molecule is. (iPhone only)

Get the MOTW App!

About Molecule of the Week

MOTW has been a popular feature on this site since 2001. Many molecules are suggested by our website visitors. Every structure is reviewed by a scientist and displayed in 3-D and flat images with a brief description.

Each week’s molecule also links to a sample record from the CAS REGISTRY, which is searched using SciFinder. Each record displays the registry number, index name and synonyms, bibliographic information, and more.