Our eyes need to stay moist all the time, in order to move around freely and to clear away dust or small foreign objects.

The glands that produce tears to keep eyes from drying out are called our lacrimal glands.

If you’ve ever been outside when it’s really windy, you may have experienced your eyes suddenly watering when the wind kicks up suddenly.

Other external factors, like strong smells or the natural chemicals that are released when we cut up raw onions, can also cause our eyes to water.

Another trigger for those lacrimal glands is a high level of emotions: most often sadness,

but feelings of pain or happiness can also make us cry.

Have you ever laughed so hard at something your eyes started to cry, like this emoji? 

When we feel very strong emotions like sadness, the part of our brain that process feelings sends signals to the part of the brain that controls our tear glands,

and a higher volume of tears are produced.

This amount is more than our natural drainage system can handle,

and the tears well up and overflow.