The Mu2e experiment at Fermilab aims to observe the charged-lepton flavor violating neutrinoless conversion of a negative muon into an electron. The conversion results in a monochromatic electron with an energy slightly below the muon rest mass (104.97 MeV). Two major elements of the detector system are the straw tube tracker and the crystal calorimeter. This paper describes the tracker and the calorimeter systems and provides experimental results obtained in the prototyping and pre-production phases.