Nonlinear optics (NLO) involves the interaction of light with matter in a nonlinear manner, leading to phenomena such as two-photon excitation, second-harmonic generation and third-harmonic generation. These techniques allow for deeper tissue penetration and reduced photodamage compared to traditional linear optical methods. Due to much confined excitation within a tiny focal volume, NLO techniques can provide high-resolution images of biological tissues, even at significant depths. Aggregation-induced emission (AIE) refers to a phenomenon where certain molecules, which are non-emissive in solution, become highly luminescent upon aggregation. This unique property is particularly advantageous for bioimaging because it reduces background noise and enhances signal intensity. The synergy between AIE and NLO can significantly improve bioimaging clarity. AIEgens can be designed to exhibit strong nonlinear optical properties, enabling their use in multiphoton excitation microscopy. This combination allows for the visualization of biological structures with high contrast and minimal background interference. Additionally, the photostability of AIEgens ensures that the imaging process can be sustained over extended periods without significant loss of signal. In this talk, I will elaborate our recent research progress on leveraging the unique properties of AIEgens and the advanced capabilities of NLO techniques to realize high-contrast three-dimensional vasculature imaging and highly sensitive detection of tumor biomarkers.