The microscopic space that exists between nerve cells is called the synaptic cleft.

Here's a breakdown:

* Synapse: The junction between two nerve cells (neurons) where communication occurs.

* Synaptic cleft: The tiny gap (about 20-40 nanometers wide) that separates the presynaptic neuron (the one sending the signal) from the postsynaptic neuron (the one receiving the signal).

* Neurotransmitters: Chemical messengers that are released from the presynaptic neuron, travel across the synaptic cleft, and bind to receptors on the postsynaptic neuron, transmitting the signal.

Think of the synaptic cleft as a very narrow bridge connecting two neurons. It's important because it allows for controlled and precise communication between nerve cells, which is crucial for the functioning of our nervous system.