Jill is studying a strange bacterium. When she first looks at the bacteria, there are $1000$ cells in her sample. The next day, there are $2000$ cells. Intrigued, she comes back the next day to find that there are $4000$ cells! Create multiple representations (table, graph, and rule) of the function. The inputs are the days that have passed after she first began to study the sample, and the outputs are the numbers of cells of bacteria.