Over the years, there have been growing interests and efforts in harnessing disorder for photonic device applications, not only to improve the performance of existing devices, but also to enable novel schemes and unique functionalities. In this seminar, I will illustrate how disorder and complexity can be harnessed for photonic device applications with a few examples. One example is a compact random spectrometer that combines high resolution with small footprint. Beyond passive devices, incorporation of disorder to a laser will reduce the spatial coherence of lasing emission and enable free-speckle full-field imaging. Furthermore, disorder can disrupt coherent nonlinear coupling between lasing modes and suppress temporal instabilities. Finally, engineering disorder for photonic devices will open up a huge parameter space for device design and optimization.