A sleep aid device for inducing and/or maintaining sleep which includes a fluid-filled mattress, a fluid pump sealably connected to the mattress, and a control module. The fluid pump modulates fluid into and/or out of the mattress, which may simulate the feel and/or sound of a human breathing. Also, the sleep aid device may include a heartbeat module which simulates the feel and/or sound of a human heartbeat. Further disclosed is a method of inducing and/or maintaining sleep by simulating the sound and/or feel of breathing and/or heartbeat, and controlling the rates of the simulated breathing and/or heartbeat to induce and/or maintain sleep.