What are the little transparent dots I see that float down when I look up into the sky?

Floaters. Posterior vitreous detachment and vitreosyneresis. These are the cause of floaters seen very commonly with aging and liquefaction of the vitreous gel in the back of the eye. If you see a large shower of new floaters, flashing lights, or a shadow on side of vision, contact an ophthalmologist immediately, as this can signal a retinal tear or detachment.
Floaters. The back of the eye is filled with a transparent gel that liquifies over time (like a bowl of jell-o that is left out of the fridge for a long time). As this happens, bits of gelbreak off and become trapped into the liquid pools. When you look at light objects you can often see these pieces floating around. If these are new or are more than usual, please see an eye doctor immediately.
Vitreal floaters. These objects are known as vitreal floaters and by and large they present no danger. As we age, the jelly that takes up the space in the middle of the eye (the vitreous) begins to break down. As this process occurs, shadows from particles in the vitreous are cast onto the retina causing the perception of floaters. I recommend a dilated eye exam once a year to make sure no other problems arise.
Normal or floaters. The gel that fills the inside of your eye can sometimes have opacities that you may see against blue background. If you have flashes or a veil like sensation or these symptoms have associated loss of vision-see your eye doctor immediately. Another answer is called the entopic phenomenon-believed to be the perception of blood flow aroundthe central part of your retina called the fovea.