Angiogenesis, inflammation and homeostasis are highly related, and the Ang/Tie system lies at the intersection of all three processes [99, 100] . The Ang/Tie system is critically important for angiogenesis during embryogenesis, but in healthy adults its function shifts toward maintenance of homeostasis and reaction to insults. Except for follicle formation, menstruation and pregnancy, angiogenesis in adults is disease related. Neoplasia-associated neoangiogenesis and neovascularization in diabetes and rheumatoid arthritis are unfavourable events, and improper angiogenesis is the subject of research in ischaemic disorders and atherosclerosis. Finally, failure to maintain homeostasis and an inappropriate reaction to injury are detrimental features in critical illness.