Will at 16 months likes to draw - but he also likes to play with the felt tipped pen. 

Here you see him drawing for a short while and then he decides that he wants to play with the pen.  He discovers that the lid is missing and  it takes me a few moments to understand his request for the lid.  

Notice how he pulls the lid off and puts it together again many times. This repeated practice of an action helps to refine his control.

You will also notice how he does not always look at what he is doing - in these moments he is relying on the information he gets from his joints, muscles and fascial system to guide his movements. 

This moving without continuous visual guidance is important for improving feed forward control. 

Even at this young age Will has learned to stabilize the paper with his left hand.  Experience has taught him to what is needed to achieve his goal and he plans his actions accordingly.

Therapists refer to this as motor or action planning. Children with coordination difficulties (DCD) often need extra help to acquire good motor plans. 

Read more:
Activities for training of fine motor control / hand actions