Animation is the process of drawing sequential pictures which, when assembled, form a moving image over time. In the past, this work was done by hand with teams of artists creating literally thousands of drawings for a cartoon, ad, or film. These days, more and more animation work is done on a computer which can speed up the process while also increasing the complexity of the images and the lengths of a film. Consequently, there has been an explosion in the field of animation, with many more people employed in it now than ever before. Strong, facile drawing skill is a must for entry into this field, as is an ability to work on the same project for an extended period of time with a team of other artists.