After children draw and experiment with scribble writing, they begin to use letters in their writing. The letters above were written by a four-year-old girl; some of the letters she wrote are in her name, and she is experimenting with their direction and placement.
This was written by a five year old; he, like the other children in these examples, is playing with random strings of letters. Children who are exposed to books and text gain the understanding that letters and words carry meaning, and they want to write as many letters as they see in books and in their environment, rather then just their name or a few letters.
This is another example of random strings of letters, and this one comes from a four-year-old. She worked on this for an extended period of time, about 15 minutes, in the writing center. In this piece, she is also writing short lines from left to right, and from top to bottom, showing her understanding of how text works.
I wanted to include an examples without letters to enter in my belief that there are multiple symbol systems that we can write. In the picture above, a four-year-old girl used the calendar in the classroom to copy all of the numbers. Writing numbers is as common as writing letters, especially when there are numbers in the environment to inspire the child. She also uses "mirror writing", which many children do for quite some time before writing the "correct" way. I have a few students this year who switch back and forth between the two depending on the situation, writing forwards one day and backwards the next.
Another symbol system that children in my classroom have been trying out a little is musical notation. The five-year-old above wrote this "song" -- when he finished he sang it for me:
One gray, Two pink
Three green, Four blue
...in ascending notes. I was quite taken by the five staff lines that he drew across the page. There are many more symbol systems that I am not mentioning here, but you get the idea!
Next will be my personal favorite: inventive spelling!