How does thermal energy transfer when a slice of pizza is warmed in the microwave? Air currents cause particles in the pizza to circulate.
Direct contact of the pizza with the oven creates heat.
Electromagnetic waves transmit heat to the pizza.
Movement of particles in the microwave generate heat.

In order for a high temperature boiler or steam engine to produce superheated water, or steam: the heat source must be greater than 100°c the water must be permitted to evaporate quickly the system must be sealed and become pressurized above atmospheric pressure the vapor pressure must be kept below 760 mm(hg)