What organisms are usually too small for you to see directly?

Microorganisms are too small for us to see directly, so we have to use a microscope to see them.

Neurotransmitters are messengers responsible for communication between neurons. they are released from synaptic vesicles and are received by receptors.  the communication is referred to as neurotransmission. the following statement is true about neurotransmitters: a. they're stored in synaptic vesicles in the axon.