Focused electron beam induced deposition (FEBID) has been demonstrated as a promising solution for synthesizing truly three-dimensional (3D) nanostructures. However, the lack of morphological feedback during growth complicates further development toward higher spatial fabrication precision. Here, we show that by combining in situ high speed atomic force microscopy (HS-AFM) with FEBID, morphologies in multistep fabrication process can be accessed. More importantly, the proposed method enables simultaneous imaging and fabrication operation, which opens new possibilities to investigate evolving mechanical properties of the deposit. The experiments indicate an exponential increase law of the mechanical resistance, meaning that a mechanically stable state establishes around 4 min after deposition.