The disclosure relates to a methods and devices for producing three-dimensional objects by a beam acting on and selectively solidifying a construction material applied layer by layer. The devices include at least one process chamber, which has a building platform on which the three-dimensional object is created, a radiation source for producing the beam, at least one beam guiding element, and a process assisting device movable above the building platform and having a first and second module with a beam guiding portion arranged between for the beam that is directed onto the building platform. Each module has at least one application device for discharging construction material and a monitoring device with at least one sensor element for sensing the applied and solidified layer of construction material.