Drawbacks of nanoparticles are poor tissue extravasation, incomplete drug release, and off-targeted delivery to the reticuloendothelial system and organs. The Law lab developed a new nanofiber platform (NFP) displaying a unique dimension (0.5 x 5 x 100 nm) different from other nanoparticles. The NFP has an excellent tumor-targeting property. It can structurally transform into 10-times larger interfibril networks, serving as in situ depot promoting weeks-long local retention. Used as a drug carrier, the NFP possesses superior therapeutic efficacy concerning disease progression inhibition. It improves the survival of animals bearing triple-negative breast cancer tumors while exhibiting a favorable toxicity profile.