A possible mechanism for setting the dark matter (DM) relic abundance is freeze-in, where the DM is produced by extremely feeble interactions of Standard Model particles. Despite the very small couplings, if the DM interacts via a light mediator then this is a predictive and detectable scenario with possible DM mass as low as ~10 keV. I will discuss the production of this DM via plasmon decay and prospects for testing freeze-in with the CMB, probes of small scale structure, and proposed direct detection experiments.
