Abstract: I will revisit the Matrix quantum mechanical description for M-theory and discuss the associated novel fundamental string sigma model that exhibits exotic nonrelativistic behaviors. Starting with this string worldsheet theory, I will build a duality web that unifies a zoo of BPS-like decoupling limits in string and M-theory, where non-Lorentzian geometry plays an important role. This duality web connects various Matrix theories to string theories that are nonrelativistic, tensionless, ambitwistor, Carrollian, etc. It is also naturally related to the Spin Matrix limit of the AdS/CFT correspondence. Finally, I will comment on the implications of this duality web for the Matrix theory/supergravity correspondence, the AdS/CFT correspondence, and flat space holography.