Simply by shining a light on the liquid crystals, the team created ripples of twisting molecules through them. The distinctive patterns in the crystals could also allow them to be used in anti-counterfeit devices, say the authors. Intermolecular forces between rod-like liquid crystal molecules mean that they usually all point in the same direction. The amount of light that passes through depends on a molecule’s alignment, revealing the time crystal’s ripples as a series of dark and bright stripes. Because the pattern changes across both space and time, the system is technically a space-time crystal, say the authors.