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Imaging through complex media is challenging because scattering results in image blurring. By introducing a fingerprint operator and applying it to the measured reflection matrix, information on a target within a complex medium becomes accessible.

In many optical systems with time-reversal symmetry, it is possible to control the output waves by shaping the input fields. Now a scheme is presented that works for multimode fibres that lack time-reversal symmetry due to thermal effects.

Using a water bath subject to a sudden vertical jolt — representing a change in the effective gravity — researchers demonstrate the concept of a ‘time mirror’, where time-reversed waves return to their point source following a downward jolt.

The challenge of reconstructing the image of an object when viewed through an opaque material is of particular importance for biological tissues. Here, the authors show that it is possible to reconstruct the image of a complex object from interference patterns of multiple wavefronts using phase-shifting interferometry.

A metamaterial-based acoustic sink has been designed to serve the purpose of absorbing the diverging waves and demonstrating three-dimensional sub-diffraction spherical sound wave focusing.

Photonic crystals efficiently control wave propagation on a wavelength scale, but this means they can become very large when long wavelengths are involved. Metamaterials made of resonant unit cells can confine and guide waves even at scales far below their wavelength.

Contrary to intuition, a disordered scattering medium can be exploited to improve, rather than deteriorate, the focusing resolution of a lens.

Membrane-based acoustic resonators of subwavelength dimensions achieve nearly perfect acoustic absorption.

Microscopy exploits light scattering to image biological tissues, but heterogeneities distort wave trajectories, creating a foggy image. A digital approach is proposed to harness these complex paths and reveal the inner structure of opaque media.

Various techniques combine light and ultrasound to study the inside of strongly scattering samples, beyond the reach of purely optical imaging. Here, Katz et al. introduce the acousto-optic transmission matrix framework that allows to control and focus light beyond the acoustic diffraction limit.

Based on the acquisition of a multi-spectral reflection matrix at a high frame rate, a fully digital microscope overcomes aberrations and multiple scattering to provide a three-dimensional image of an ex vivo opaque cornea at a resolution of 0.29 μm and 0.5 μm in the transverse and axial directions, respectively.

Indoor sound fields are disordered due to reflections and multiple scattering, which scrambles acoustic communication. Here, based on tunable metasurfaces and communication theories, the authors demonstrate multi-channel, multi-spectral, cross-talk-free acoustic communication in a room.

Double-positive αβ thymocytes undergo negative selection on thymic epithelial cells. Ziegler and colleagues show that TGF-β limits numbers and function of medullary thymic epithelial cells, thus influencing the resultant T cell repertoire.

A new method called functional ultrasound (fUS) is reported that allows imaging of transient changes in blood volume in the whole rat brain with a spatiotemporal resolution not attained by other functional brain imaging modalities.

Ultrasound is a flexible and powerful medical tool. Yet, brain imaging has remained elusive so far for ultrasound due to the blurring induced by the skull. Here, a 3D non-invasive approach is proposed to make the skull digitally transparent and image brain tissues at unprecedented resolution.

Currently a cell-resolution map of the human cornea can only be obtained in the clinic with a confocal microscope in contact with the eye. Here the authors develop a full-field/spectral-domain OCT microscope (FF/SD OCT) to enable cell-level detail of the entire ocular surface, as well as blood flow and tear dynamics.

Existing classical wave analogues of topological insulator are physically wavelength scaled, limiting potential applications. Here, Yveset al. show complex topological crystalline properties in spatially ordered metamaterials with deep subwavelength resonant elements on specific lattices.

Metamaterial lenses enable super-resolution imaging of structures, beating the diffraction limit. Lemoultet al. propose a resonant metalens based on plasmonic nanorods that uses polychromatic light to achieve sub-diffraction limit focusing and imaging in the visible spectral region.

The combination of ultrasound and optics, together with statistics, now permits light focusing and imaging deep inside strongly scattering media at the optical diffraction limit.

Perfect orthogonality can be imposed on wireless communication channels by using reconfigurable metasurfaces to tune the disorder of their propagation environment.

Diffraction-limited imaging in a variety of complex media is realized based on analysis of speckle correlations in light captured using a camera phone.

Scattering of light is usually seen as an impediment to focusing and imaging. This article reviews the recent progress of how strongly scattering media can be used to focus, shape and compress waves by controlling the many degrees of freedom in the incident waves.

Robust evidence that creativity is tied to the capacity to dynamically switch between brain networks supporting spontaneous and controlled cognition.

A negative refractive index, a property that does not exist in natural materials, can be produced in so-called metamaterials by combining two building blocks; here it is shown that it is possible to design and fabricate a metamaterial with a negative refractive index that consists of only one type of building block by taking advantage of its crystalline structure, and this approach is demonstrated through an acoustic superlens.

Exquisite control of loss and gain in non-Hermitian systems allows waves to propagate in unusual and useful ways. Here, unidirectional amplification is achieved in an acoustic metamaterial by dynamically varying the gain and loss with modulation phase delay between different metaatoms.

A matrix approach for seismic imaging reveals the plumbing system of La Soufrière volcano, Guadeloupe. Seismic noise correlations yield a reflection matrix whose physics-based post-processing allows an optimized focusing through volcano heterogeneities.

Dynamic full-field optical coherence tomography (D-FFOCT) is used for live cell imaging of primary porcine retinal pigment epithelium (ppRPE) cultures and human induced pluripotent stem cell-derived RPE (hiRPE) cultures, allowing non-invasive realtime access to organelles and cytoskeleton dynamics in RPE cells.