Picking up toys and dropping them again is fascinating for babies.
Not only does the game provide long stretches of entertainment for babies (have you ever seen a baby tire of the “put it in and take it out again” game?) but the skills involved in picking up and letting go of an object are very important.
Selecting an object or toy of interest requires a lot of concentration from baby as she is practising the ability to choose. Grasping that object requires fine motor skills (using the small muscles in the fingers), and gross motor skills (using the big muscle of the arm) to hold tightly onto the object selected.
Then, dropping the object on, or into something else requires hand-eye coordination as they consciously send signals from the brain to the fingers to let it go. That really is a lot of effort for a little baby!
Encourage this by giving her smaller objects to drop into larger ones. Small plastic containers can be picked up and dropped into a large metal mixing bowl or pot, and baby will enjoy trying to stack and sort them as well. Help her sort by colours, sizes and shapes and clap as she drops them noisily into the bowl.