Felines are better socialized and happier adult Cats, when they stay with their mothers and littermates for at least 12 weeks. Never accept a Kitten at 8 weeks old... they are just not ready to be on their own at that age. Often it is a "Kitten Mill" that will sell Kittens at an inappropriate age, because for them it is about money and not about the Cats or about you. However, if a Kitten is found and is motherless, by all means, do everything possible to help - no matter what it's age.
We know that Kittens are born with their eyes still closed and not yet developed to see. At about 9 days old, they open their eyes for the first time. For the first 3 or 4 weeks they can only nurse and are completely dependant on their mother. As early as 3 weeks old, they will begin to be interested in other souces of food and may even start to use a litter box. There is no "training" needed for litter box use; Cats, in general, will naturally want to hide their excrements. This is when an inexperienced owner or Breeder can inadvertantly cause harm to Kittens. Kittens will try to eat their mother's wet or dry food and not yet understand that crunchy litter is not food. Clay litter, if consumed, will "clump" and bind in a Kittens intestines and it can quickly cause death. Click HERE to review safe and healthy litter choices.
At about 4 to 5 weeks old, Kittens can walk and will begin to explore beyond their den. Kittens are brave little souls and rush about as if they own the world. From 6 to 9 weeks old, Bengal Kittens usually go through the "Grey Fuzzies" stage. It is a trait from their wild ancestry and they temporarily have longer grey-ish fuzz that (unfortunately) defusses and disguises their beautiful markings and coloration. Happily, they will soon grow out of this pelt stage.
Finally, at 12 to 14 weeks old, Kittens are ready to leave the nest. They are full of energy and ready to explore. The physical changes, like changing eye color (from Kitten blue to green or gold), the smoothing of their pelt, pattern definition and pelt colorations happen slowly from 12 weeks to 12 months or so. As Kittens mature, they also build muscle and their conformation is refined into their adult attributes. Generally, Bengal Cats will live for 18 to 20 years of age. Certainly, the quality of food and the care that you give them will keep them healthy and happy for many years of wonderful companionship.