When you think controls you need to separate your thoughts into Set-up Controls and Experimental Controls. Set-up Controls consist of samples needed to balance out the different fluorochromes and to choose starting baseline voltages if you are not using optimal PMT voltages. To properly compensate for your experiment you will need to bring an unstained Control (your cells with NO fluorochromes) which we may not include in your set-up, but will want to see, and then a Single Color Control for each fluorochrome that you are using in your experiment. The instrument is set up using these controls for compensation; without them we would be guessing at these critical settings. These controls are manditory and you will need them every time you set up your experiment. Experimental Controls would be determined by the individual user, as in a Positive and Negative control, Stimulated vs. Unstimulated, etc. We can help you with these experimental design questions if you need help.