Why do babies cry so much?

Some babies are born with colic.. Look that up if you want. Also new mothers and fathers that have never had any children may feel that their baby cries alot, but in reality considdering they r new at parent hood, they might not understand right away what their baby needs. Babys almost always cry because they need something whether it be a diaperchange, a feeding, to be held, to be burped, if they are sick. Babies cant speak, so thats what they do they cry. Also babies cry when they have gas, it hurts their tummies. How old is ur sister? Did she have a baby?