Most of this article will apply to babies older than 4 months. Babies younger than four months still have developing circadian rhythms, and some might even still be balancing out from Day/Night Confusion. Circadian rhythms are internal clocks that regulate the sleep-wake cycle. In young babies, these rhythms are still maturing, which means they may not be able to sleep through the night as consistently as adults do. It also means that your little one may not have the same concept of Day or Night that you do. This will come over time, and if you are focusing on healthy sleep foundations, then days and nights will separate and become more balanced over time.