When Leonardo da Vinci immortalized Lisa del Giocondo with his portrait of her in 1503, he created her famously subtle smile and lifelike flesh by using deliberately irregular brushstrokes. His masterpiece, the “Mona Lisa,” not only became one of the most familiar images in history, but it also created a study of light that seemed impossible for any painter to improve upon. Five hundred years later, an international group of researchers who specialize in the study of light took on that challenge. Based in Tianjin University, the Beijing Institute of Technology, Rowan University, the University of Missouri, Qingdao University, Shijiazhuang Tiedao Univer- sity, and Beijing Jiaotong University, the collaborators developed an acoustic metasurface-based holography technique that reconstructs a digital image as a hologram before applying deep learning algorithms to iteratively improve the image quality. A team of researchers combined deep learning algorithms and metasurface technology to reconstruct one of history’s most iconic images as a highly detailed hologram. Courtesy of Xuan-Bo Miao/Tianjin University. To illustrate their novel technique, the researchers needed an iconic image immediately familiar to anyone on the planet, which led them to da Vinci’s “Mona Lisa.” Metasurfaces, which are 2D optical materials that manipulate lightwaves via nanoscopic surface structures, offer interesting new capabilities for holographic processes. Metasurface-based holograms enable pixel-level control over the phase and amplitude of lightwaves that interact with their surface to create an image that is based on optical interference. The researchers further developed a neural network-based algorithm to tailor the structures of their metasurface to iteratively diminish inconsistencies between the original image and its holographic version. Applying their holographic method to the “Mona Lisa,” and especially her left eye, allowed the researchers to reconstruct the image as an optimized hologram with significant detail. Their image was 2D, though the technique can also create 3D images. Da Vinci’s mastery of brushstrokes, paint, and pigment achieved a study of light that resisted improvement for 500 years. It took the study of lightwaves, metasurfaces, and deep learning algorithms to finally restore his iconic image to its original medium.