A biomarker, or biological marker may be a measurable indicator of some biological state or condition. Biomarkers area unit usually measured and evaluated to look at traditional biological processes, unhealthful processes, or pharmacological responses to a therapeutic intervention. Biomarkers area unit utilized in several scientific fields. Biomarkers used for drugs, or exactness drugs, area unit a region of a comparatively new clinical toolset. they are categorized in three primary ways that in line with their clinical applications they are classified as molecular biomarkers, cellular biomarkers, or imaging biomarkers. All three kinds of biomarkers have a clinical role in narrowing or guiding treatment selections and follow a sub-categorization of being either prophetic, prognostic, or diagnostic.