Neovascularisation is the formation of new blood vessels from pre-existing vasculature, typically occurring in response to tissue hypoxia or injury. It is clinically significant because it can restore blood supply to ischaemic tissues but may also contribute to pathological processes such as tumour growth or retinal diseases. A key example is diabetic retinopathy, where abnormal neovascularisation can lead to vision loss through vitreous haemorrhage or retinal detachment.