In her post, Alla Kholmatova discusses how her team has determined what’s a molecule and what’s an organism in their atomic design system. It’s a thoughtful post that discusses some of the challenges around determining whether to define a component as a molecule or organism.
In atomic design, molecules are simple components, while organisms are relatively complex components. My general rule of thumb is that if you break a component down and get basic tags (such as an image, heading, paragraph, button, etc), it’s a molecule. If you break the component down and get smaller components (social share lists, cards, media object, etc) it’s an organism.