Diversification represents the cornerstone of modern portfolio theory (MPT), developed by Nobel laureate Harry Markowitz, and remains the most widely accepted risk management strategy among institutional investors, wealth managers, and individual investors globally. The core principle of diversification is that different assets perform differently under various economic conditions—when stocks decline, bonds may rise; when domestic markets stagnate, international investments may thrive—creating a portfolio where losses in one area can be offset by gains in another. In overseas investment markets, effective diversification extends beyond simply owning multiple stocks; it encompasses asset allocation across equities, fixed income, commodities, real estate, and alternative investments; geographic diversification across developed and emerging markets; sector diversification across industries with low correlation; and even currency diversification to mitigate foreign exchange risk. For US and European retail investors, diversification strategies vary by risk tolerance and investment horizon: younger investors with long time horizons might hold 80-90% of their portfolio in globally diversified equities, while those approaching retirement typically shift toward 50-60% fixed income investments to reduce volatility. Modern investment vehicles like ETFs and mutual funds have made sophisticated diversification accessible to individual investors with even small amounts of capital, allowing them to gain exposure to hundreds or thousands of assets with a single investment. However, investors must avoid common diversification pitfalls, including over-diversification (which can dilute returns without reducing risk proportionally), concentration in similar assets (like owning multiple tech sector ETFs that all decline together), and ignoring correlation coefficients between assets. Successful diversification requires periodic portfolio rebalancing to maintain target asset allocations, particularly after significant market movements that can skew original risk profiles. For financial practitioners and individual investors alike, diversification is not merely an optional strategy but a fundamental practice for achieving consistent long-term returns while managing the inherent risks of investing in global financial markets.