The disclosure provides a device and method for rapidly changing temperatures of a sample. An example of the device include: a first plate; a second plate; and a heating/cooling layer disposed on either the first or second plate. The first plate and the second plate face each other and are configured to receive a fluid sample sandwiched therebetween. The method includes depositing the fluid sample on one or both of the two plates, pressing the plates to form a thin layer of the sample, and changing and/or maintaining the temperature of the sample. The device or method can be used in, for example, PCR.