The Hilbert-Huang Transform (HHT) is a way to decompose a signal into so-called intrinsic mode functions (IMF), and obtain instantaneous frequency data. It is designed to work well for data that are nonstationary and nonlinear. In contrast to other common transforms like the Fourier Transform, the HHT is more like an algorithm (an emperical approach) that can be applied to a data set, rather than a theoretical tool.Almost all the case studies reveal that the HHT gives results much sharper than any of the traditional analysis methods in time-frequency-energy representation. Additionally, it reveals true physical meanings in many of the data examined.