This document discusses various types of biological samples that can be collected from humans for diagnostic purposes. It defines a biological sample and provides examples such as excretions, secretions, tissues, and cell cultures. The document then describes sample collection procedures for common samples like urine, blood, stool, sputum, and exudates. It emphasizes the importance of sample quality and outlines the steps needed for proper collection, transport, processing, and analysis of samples to accurately diagnose patients.