The idea of creating drawings on paper at the onset of the Renaissance was strictly a practical matter; as artists such as Da Vinci became increasingly interested in their own creations rather than simply copying finished works, it became necessary to make some changes to the creative process. The drawings, then became the beginning of a new project, a way to begin planning on paper, through a set of quick sketches that might approximate what a professional writer does when he or she "brainstorms" random ideas and words on paper. This technique was particularly useful when one aimed to produce a sculpture or painting of a human figure, because these sketches allowed for unrestricted exploration of a human's muscles or skin tones, for example, or the folds of his or her clothing, or the deconstruction of one's facial expressions.
These quick sketches came to be followed by a more formal series of studies of the subject to be painted or sculptured, and then a set of full-scale drawings, sometimes referred to as cartoons, was produced. On a more practical note, drawings came to be part of formalized contracts drawn up between an artist and his patron; with a drawing as part of the contract documents, disagreements on the vision of a painting, sculpture or architectural construction, were much less likely to occur.
Although drawings initially became popular as a practical part of the planning process of an important work, drawings themselves are often now viewed as highly artistic and worthy of our contemplation as much as the finished works might be. One need only look for a few minutes through the drawings of the notebooks of people like Leonardo Da Vinci to see the genius at work in what were intended to be casual sketches as a prequel to something greater.