The two most famous bubbles of the twentieth century, the bubble in American stocks in the 1920s just before the Wall Street Crash of 1929 and the following Great Depression, and the Dot-com bubble of the late 1990s, were based on speculative activity surrounding the development of new technologies. The 1920s saw the widespread introduction of an amazing range of technological innovations including radio, automobiles, aviation and the deployment of electrical power grids. The 1990s was the decade when Internet and e-commerce technologies emerged.