The document discusses factors that affect embryo temperature during incubation. It finds that machine temperature does not equal embryo temperature, as embryo temperature depends on a balance between heat production and heat loss. Heat production is influenced by developmental stage, physical traits, biological traits like breed and egg size, and environmental factors like oxygen levels. Heat loss depends on evaporation, which is affected by humidity and air temperature, and heat transfer, which depends on temperature differences, air properties, and velocity. Maintaining a constant eggshell temperature close to 37.8°C is important for optimal embryo development.