1. Physiological reasons 1.1 Hungry babies have small stomach capacities and limited digestion and absorption capabilities, so they need to eat frequently. If the baby does not get enough food within the prescribed time, he will feel hungry and cry. 1.2 Defecation: Infants’ intestinal functions are imperfect, and poor defecation can cause discomfort and pain. When babies need to have a bowel movement, they may cry to express discomfort. 1.3 Pain Since their physiological development is not yet fully mature, babies are very sensitive to various stimuli. Teeth eruption, injections, vaccinations, etc. may cause discomfort and pain to your baby. 2. Psychological reasons 2.1 Desire for care Babies are naturally thirsty