PyCharm's code cells are a way to separate and execute different portions of a large Python program sequentially. If you are familiar with Jupyter notebooks, code cells are, in essence, the bare-bones version of executing Python code (if you're not familiar with Jupyter notebooks, then don't worry—we will be discussing them in the next chapter). This ability is specifically valuable in scientific computing projects when different sections of a program are run in order, allowing programmers to follow the logic of the program in an incremental way.