The importance of sleep in the development is only now beginning to be understood: sleep and established sleep cycles have an important role in the normal neurosensory and cortex development. The biological basis of sleep organization has been highlighted by several studies however environmental differences can affect the sleep patterns in preterm infants in the NICU. Sleep disorders are related to several physiological conditions but it is important to know the relationship between sleep organization and neurocognitive and socio-emotional outcomes. From the recent literature it is possible to find out potentially better practices that preserve and promote infant sleep in the NICU.