A world-first photonic time crystal can reshape light almost instantly, opening a path toward ultrafast optical technology. Creating photonic crystals could lead the way to the closing of this gap.” From Photonic Crystals to Photonic Time CrystalsConventional photonic crystals are nanostructured materials arranged in a repeating optical pattern (like a lattice) that influences how photons move. Earlier experiments by the same research team showed that changing temperature or applying magnetic fields could modify how photonic crystals trapped light. “By extending photonic crystals from space to time, we open a new dimension for light control—and a novel path toward amplification and lasing.