How do neurons find each other?
Q: We know neurons can organize into very complex networks, but how?

The answer is your first guess: Neurons find other target neurons with specific chemical signals.

Q: What are the names of said mechanisms?

This process is called axon guidance, by which the growth cones of developing axons are directed to reach their targets. This process depends upon a slew of cellular and molecular cues. The first axons to grow in any particular brain region are called pioneer axons and are the most dependent upon these cues. Later axons are able to follow (and diverge from) previous axons by the interaction of cell adhesion molecules on their surfaces. Dendritic development is also important for your question, but dendrites tend not to travel as far.

Here are some of the molecules that we know to participate in axon guidance:


Cell adhesion molecules and substrate adhesion molecules, including IgSF CAMs and cadherins
Some chemokines, e.g. CXCL12
Netrins, ephrins, and semaphorins
Slits, via the Slit-Robo cell signaling pathway
Developmental morphogens, e.g. Wnts and Hedgehog


The list goes on, and this is an area of active research. Each of these cues is recognized by one or more specific receptors on the developing neuron, which upon recognition of the ligand molecule either attracts or repels the axon from (or both, depending on the context). Recognition can function either short-range (by direct contact with a ligand) or long-range (e.g. by detection of a concentration gradient), depending on the molecular cue.

For more information, you may want to read Sanes et al., Development of the Nervous System.