What age do children start using their thumbs to aid them in grasping objects?

Children typically begin using their thumbs to aid in grasping objects around 8 to 12 months of age. This development coincides with the emergence of the pincer grasp, where they can pick up small items using their thumb and forefinger. By 12 to 18 months, their ability to use their thumbs effectively continues to improve, allowing for more refined manipulation of objects.