This chapter explores the concept of precision medicine, also known as personalised or P4 medicine, which is based on the principles of predictive, preventive, personalised and participatory healthcare. It emphasises the grouping of patients based on disease risk and response to treatment through diagnostic tests, leading to more effective and targeted treatments. The integration of systems medicine, which views the human body as an interconnected system of biological and environmental factors, is critical to advancing precision medicine. Pioneering work in systems biology has laid the groundwork for a deeper understanding of complex diseases. This chapter highlights the role of big data and artificial intelligence (AI) in enhancing the capabilities of precision medicine, particularly in oncology, cardiology and diagnostics. It discusses current applications of AI, challenges such as data integration and ethical concerns, and the need for clinical validation. The future outlook suggests that precision medicine will increasingly complement traditional medicine, fostering a more personalised and efficient healthcare system. Ultimately, the synergy between precision and traditional approaches is proposed as essential to improve patient outcomes and reduce healthcare costs.