This category brings together routine and widely used laboratory investigations that form the foundation of medical checkups and diagnosis. Each article explains the purpose of the test, what is being measured, how the sample is collected, and how results are interpreted. Covering tests such as complete blood count (CBC), urine examination, blood sugar, lipid profile, ESR, and other basic panels, this section is designed to help patients, students, and healthcare professionals clearly understand the role of these common tests in maintaining health and detecting disease early.