Systematic noises come from consistent errors in the experiment that can be identified and potentially corrected during data processing. For example, if there are errors in handling the liquids or inconsistencies in how the probes are spotted on the microarray, these can introduce systematic noise. Systematic noise can also arise from variability between different scanning devices and differences between batches of samples or reagents. Another source of noise is inherent noise. This noise is unavoidable and comes from the natural variability in molecular interactions, even if everything in the experiment is done perfectly. Poisson noise and shot noise from image sensors are types of inherent noise. Unwanted variations or errors can occur at each step of the process (such as during RNA extraction, cDNA synthesis, or hybridization) which can impact the quality of the final data.