Field's Stain, often used in hematology, is a rapid staining technique for blood smears, particularly useful for screening malarial parasites. It's a version of the Romanowsky stain, similar to Giemsa or Leishman stains, and utilizes a combination of methylene blue and eosin to differentiate cellular components. Field's Stain A primarily contains methylene blue and Azure 1 in a phosphate buffer, while Field's Stain B contains eosin.