Ultrafast control of anisotropy Single-molecule magnets are able to store information through their magnetic anisotropy, making them very promising systems for memory applications. Now, femtosecond-laser-initiated molecular dynamics that modulate magnetic anisotropy have been observed, paving the way for operation on ultra-fast timescales. Twitter: @rx_collet Single-molecule magnets (SMM) represent a molecular approach to nanomagnets. These metal-organic compounds exhibit-below a certain blocking temperature-magnetic hysteresis at the molecular scale and retain magnetisation in the absence of a magnetic field. SMMs have a bistable magnetic ground state and the associated energy barrier arises from a combination of a high-spin ground state and significant axial anisotropy of that ground state, making them promising candidates for the next generation of information storage devices. Since the first report on a single-molecule magnet, 1 efforts in this field have primarily focused on raising the operating temperatures in order to enable applications in magnetic memory. 2 Among strategies for increasing the scope of applications for SMM, several groups have explored various ways to control their magnetization via an external stimulus, such as pressure, electric potential, light or the coordinating solvent. 3 Now, writing in Nature Chemistry, Johansson and colleagues have explored the ultrafast dynamics of magnetic control when initiated using femtosecond light excitation.