  Thanks to the latest advancements in wavefront shaping, optical methods have
proven crucial to achieve imaging and control light in multiply scattering
media, like biological tissues. However, the stability times of living
biological specimens often prevent such methods from gaining insights into
relevant functioning mechanisms in cellular and organ systems. Here we present
a recursive and online optimization routine, borrowed from time series
analysis, to optimally track the transfer matrix of dynamic scattering media
over arbitrarily long timescales. While preserving the advantages of both
optimization-based routines and transfer-matrix measurements, it operates in a
memory-efficient manner. Because it can be readily implemented in existing
wavefront shaping setups, featuring amplitude and/or phase modulation and
phase-resolved or intensity-only acquisition, it paves the way for efficient
optical investigations of living biological specimens.
