After the sample is obtained, it has to be processed by different methods depending on the nature of the sample. Liquid samples, such as blood, are extracted and dried out, while solid samples must be dehydrated using a different combination of alcoholic compounds.[2] The tissue must also be stained, usually with haematoxylin and eosin, a pair of colorants that identify the acidic-basic nature of the cells.[1] After this treatment the samples are analyzed under a microscope, which can be optical or electronic, to determine if the sample is normal or pathological.[2]