Abstract: Disclosed herein include methods, compositions, and kits suitable for use in dynamic non-destructive imaging. The non-destructive imaging can be nonlinear ultrasound imaging. There are provided, in some embodiments, nucleic acid compositions encoding gas vesicles (GVs) capable of producing nonlinear ultrasound contrast upon expression in a prokaryotic cell (e.g., a probiotic bacterial cell) or a eukaryotic cell (e.g., a therapeutic mammalian cell).