life·blood 
/ˈlaɪfˈblʌd/ noun
/ˈlaɪfˈblʌd/ noun [noncount] 1 : the most important part of something : the part of something that provides its strength and energy
▪ The town's lifeblood has always been its fishing industry. ▪ The neighborhoods are the lifeblood of this city. 2 literary : a person's blood
▪ the lifeblood that flows through his veins
▪ The town's lifeblood has always been its fishing industry. ▪ The neighborhoods are the lifeblood of this city.
▪ the lifeblood that flows through his veins
