Blood is symbolically sacred across religions. Ancient sacrifices with blood were gifts to the gods. The Bible equates blood with life, influencing Jehovah’s Witnesses and Kosher/Halal practices. Catholicism venerates Jesus Christ’s blood as a sacrament. In ancient civilizations, blood symbolized life, lineage, and vitality. Egyptians associated blood with Shesmu, offering wine as a symbol. Herodotus emphasized familial blood ties. Chinese medicine linked blood to Qi, nourishing tissues and sustaining vital energy. In ancient cultures, blood symbolized life and individuality. The Renaissance introduced “Humanism,” fostering curiosity and scientific observation. Leonardo da Vinci played a pivotal role in studying anatomy with a mechanistic approach, analyzing organs, systems, fluid mechanics, and producing plausible hypotheses about blood circulation. Though criticized for reducing anatomy to mechanical models, his work broke ancient dogmas and laid the foundation for experimental physiology. Leonardo’s insights, though unfinished, influenced modern physiology and inspired William Harvey’s discoveries on blood circulation, advancing medical knowledge.