Sample preparation is the process where a representative piece of material, chemical or substance is extracted from a larger amount, bulk or batch for subsequent analysis. Representative samples are selected to accurately reflect the larger group and represent the characteristics of the whole material. Ideally representative samples are homogeneous or similar in nature, but when that is not possible, the best attempts must be made to achieve samples which represent the majority of the characteristics of the larger grouping. The preparation of samples is one of the most important steps in analytical methods for many reasons, including the fact that some materials cannot be analyzed in an in-situ condition (such as proteins, DNA and RNA). Some samples have interfering substances and species that can produce faulty results. Sample preparation can include many processes, from reactions or treatment with chemical agents, to filtration, dilution, and extraction.