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It is shown that for thermodynamics and statistical physics to be internally consistent, Gibbs’ original—rather than Boltzmann’s widely used—definition of entropy needs to be adopted. Consequently, negative absolute temperatures are strictly forbidden, and cold-atom gases are unlikely to be laboratory analogues to dark energy.

A generalized theory is provided for the quantitative description of wrinkling morphologies and of the transitions between surface patterns in curved elastic bilayer materials.

Active fluids consist of self-driven particles that can drive spontaneous flow without the intervention of external forces. Here Woodhouseet al. show how to design logic circuits using this phenomenon in active fluid networks, which could be further exploited for autonomous microfluidic computing.

Wrinkling of cell nuclei is associated with disease. During development, the nucleus behaves like a sheet of paper and the wrinkling amplitude can be manipulated without changing its pattern.

Brownian motion in a feedback-controlled optical trap provides a minimal experimental realization of a Szilárd engine, confirming fluctuation theorems and demonstrating the importance of spontaneous symmetry breaking in small thermodynamic systems.

Spatiotemporal transcriptomes during multicellular development of Bacillus subtilis swarms reveal supra-generational cooperation.

Reconstructing system dynamics on complex high-dimensional energy landscapes from static experimental snapshots remains challenging. Here, the authors introduce a framework to infer the essential dynamics of physical and biological systems without need for time-dependent measurements.

The organization of small clusters of connected cells confined to an egg chamber during early development can be mapped onto a tree packing problem. Entropically preferred packing configurations are shown to arise more readily in experiment.

Hydrodynamic coupling induces a vortex state in bacterial populations. Microfluidic experiments and modelling now demonstrate that lattices of these vortices can self-organize into patterns characterized by ferro- and antiferromagnetic order.

Formulating a consistent framework for relativistic thermodynamics has been a subject of controversy over the past century. A new approach for defining thermodynamic quantities makes predictions that are, in principle, testable, and which might lead to a natural extension of thermodynamics to general relativity.

A synthetic cell-cell adhesion logic using swarming E. coli with 4 bits of information is introduced, enabling the programming of interfaces that combine to form universal tessellation patterns over a large scale.

Experiments show that swimming starfish embryos spontaneously assemble into large chiral crystals that exhibit self-sustained chiral oscillations and unconventional deformation responses characteristic of odd elastic materials.

Whereas transitions from solid- to fluid-like states in systems of active particles have received much attention, the characterization of phase transitions in active fluids with self-organized vortices so far has remained elusive. James et al. take us on a numerical tour de force from active turbulence to active vortex crystals.

A quantitative description of sound wave propagation in suspensions of self-propelled colloidal particles is achieved by combining microfluidics, video microscopy and theory.

Co-localizing chromatin modifications and regulators can exert a combinatorial effect on chromatin structure and function. Here the authors describe reChIP-seq and normR to identify co-localizing proteins in an unbiased genome-wide manner.

A macroscopic analogue of a spin system is shown to emerge in an ensemble of droplets bouncing on the surface of a vibrating bath, revealing symmetry-breaking phenomena such as ‘magnetic’ ordering.

Single-cell tracking of up to 10,000 bacteria reveals the structure and dynamics of 3D biofilms—providing evidence to suggest that both local ordering and global biofilm architecture emerge from mechanical interactions.

Activity in certain living systems can lead to swirling flows akin to turbulence. Here, the authors connect the dynamics of topological defects in starfish oocyte membranes to vortex dynamics in 2D Bose–Einstein condensates.

Single-cell imaging analysis shows that translation-inhibiting antibiotics disrupt Vibrio cholerae biofilm structure and enable entry of bacteriophages and intruder cells.

Active matter locally dissipates energy to produce systematic motion. This Perspective highlights proliferation as a special type of activity that breaks particle number conservation and thereby gives rise to a unique set of collective phenomena characteristic of life.