The human brain function is certainly one of the most amazing phenomena known. All behavior is the result of the brain function. The 100 billion nerve cells are the home to our centers of feelings and senses, pleasure and satisfaction; it is where the centers for learning, memory and creative work are located; where laughing and crying areas and the centers of our mind are. Our cognitive functions, such as thinking, speaking or creating works of art and science, all reside within the cerebral cortex. One of the tasks of the neural science is to explain how the brain marshals its millions of individual nerve cells to produce behavior and how these cells are affected by the environment.1 The brain function still remains shrouded in a veil of mystery. But what is known is that over 99 percent of the human neocortex is produced during the fetal period.2 Owing to the employment of state-of-the-art methods and techniques in prenatal investigations, a growing pool of information on the development of the central nervous system (CNS) and behavioral patterns during intrauterine life has been made available. This review outlines these events, along with the development of the fetal sensory system and circadian rhythms, the senses of vision and hearing, fetal learning and memory, and long-term effects of fetal stress on behavior. In brief, this review offers a glimpse of the fascinating world of the intrauterine life.