The first apical layer of the cerebral cortex is also called as the molecular layer, I could not find the exact reason of the naming.
What I found:
Molecular alongside its primary meaning in chemistry can also mean:
of or relating to individual or small components
And if you only stain the neuron somas, you can only see some scattered neurons in this layer. Maybe this is the basis of to the naming.
What does molecular exactly mean in this context?
Is this adjective used widely in anatomy with the same meaning?