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It is wellknown that classical mechanics must be modified to accurately treat interatomic interactions; not so wellknown is the fact that standard thermodynamics must also be changed on a similar length scale. The theory of smallsystem thermodynamics was originally developed by Terrell Hill to describe isolated nanoparticles and individual molecules, but we find that this â€œnanothermodynamicsâ€ also provides a basis for understanding nanometersized fluctuations inside bulk materials. One result is a nonlinear correction to Boltzmannâ€™s factor. The mechanism may be attributed to finitesize effects in the laws of thermodynamics: total energy is conserved by including Hillâ€™s subdivision potential, net entropy is maximized by coupling to the thermal bath, and/or similar states are treated using the statistics of indistinguishable particles. The nonlinear correction provides a common basis for several empirical formulas that have been used to characterize the dynamics of complex systems, including stretchedexponential relaxation, superArrhenius activation, nonclassical critical scaling, and 1/f noise. I will emphasize how specific models based on nanothermodynamics yield these simple formulas, plus deviations from the formulas that match the measured behavior in many materials. Host: Sebastian Deffner 