The vitreous humor, or often just “vitreous”, is a clear gel that fills the gap between your retina and lens, helping maintain the round shape of your eye in the process. This gel is about 99% water and 1% mostly consisting mostly of a network of hyaluronic acid and collagen. Hyaluronic acid ends up retaining water molecules. Over time though, this network breaks down which results in the hyaluronic acid releasing its trapped water molecules. When this happens, it forms a watery core in your vitreous body.
As you age, pieces of the still gel-like collagen/hyaluronic acid network will break off and float around in this watery center. When light passes through this area, it creates a shadow on your retina. This shadow is actually what you are seeing when you see the eye floaters.
Children and teenagers almost never experience these types of eye floaters as there must first be some deterioration of the gel-like substance in their eye for these floaters to appear. However, they do still sometimes experience a certain type of eye floater that often appears more like a crystallized web across their vision. These floaters aren't found in the vitreous humor like the other floaters. Instead, they are found in the Premacular Bursa area, right on top of the retina. These floaters are microscopic in size and only appear as big as they do because of their proximity to the retina.