The eyes.

It's said that the eyes are the gates to the soul, and I think they always mean the ones that are blue or green, even though those are pretty I think the most beautiful ones are the ones that are so dark that you wouldn't be able to look pass them, metaphorically speaking of course.

The eyes provides us the ability of the vision and process the details of what we see, and as well as enabling several photo response function that are independent of vision. Eyes detect light and convert it into electro-chemical impulses in neurons. It is a complex optical system which collects the light of the surrounding environment, regulates its intensity through a diaphragm, focuses it through an adjustable assembly of lenses to form an image, the it converts this image into electrical signs that are transmitted to the brain through pathways that connect the optic nerve with the visual cortex of the brain.

The human eyes are located in the head, in our skull we have two big cavities and each one of our eyes uses one. The adult eye has an anterior to posterior diameter of 24 millimeters, a volume of sic cubic centimeters and a mass of 7.5 grams.

There are a lot of problems you can have in your eyes, like with age the sight gets worst gradually. There are also changes of significance in non diseased eyes like the sizes in the components of the eye are different that the normal ones. There are certain ocular diseases that can come from STDs, like herpes and genital warts, if there is contact between the eye and the area of infection.

For good care of the eyes you can quit smoking to prevent cataracts, wear sunglasses to prevent the UV lights from the sun and it's also a good idea to not look at screens for too much time or without a other lights in the room.