This is an introductory overview of neural networks. The subject is now divided into two tracks, artificial neural networks (ANNs) and computational neuroscience (CNS). Artificial neural networks are being applied in finance, industry, and commerce. Computational neuroscience attempts to model the brain, from the analysis of a single living nerve cell to the study of consciousness and self-consciousness of the whole brain. There is no doubt that neural networks will enter into a new regime of application and explanatory power in the next millenium.