Fine-needle aspirations have two main purposes: diagnostic and therapeutic. Proper needle placement is essential to harvest a good cytologic sample for microscopic diagnosis. Cytology is the examination of a single cell type which allows clinician to screen a patient for cancer, to rule out infectious organisms or other cellular abnormalities. Correct needle placement aids in both therapeutic centesis and diagnostic sampling/centesis. Ultrasound imaging allows the clinician to better understand the target in many ways that are not available with routine physical examination or conventional radiographs or advanced imaging techniques such as CT or MRI. Ultrasound guidance can also assist in a more thorough sampling of a palpable nodule or mass or regional LN in most cases. This is a prerequisite for the US-guided HOW on Saturday that covers in plane and out of plane guidance, FNA and needle biopsy; abdominocentesis, thoracocentesis, and pericardiocentesis; and vascular access (placement of intravenous catheters) including the Seldinger technique.