Tears trickling down the cheeks
Lachrymation refers to the body's process of producing tears, which clean and lubricate the eyes.
The word lachrymation may also be used in a medical or literary sense to refer to crying.
Crying is increased lachrymation due to emotion, with the result of tears in one's eyes, possibly trickling down the cheeks, in some cases accompanied by characteristic sobbing sounds.
The emotion is often sadness, but can also be joy, etc.
Babies cry a lot in case of general discomfort.