Access to atomic processes on surfaces, which are in general thermally activated, has been achieved by developing scanning tunneling microscopy (STM) for variable sample temperatures (5 K - 700 K). Application to metal epitaxy opened up an unprecedented microscopic view of nucleation and aggregation. The instrument works in UHV and combines a liquid helium flux cryostat for sample cooling with a "beetle type" STM . Vibrational damping during STM operation is achieved by suspending the STM on CuBe springs, combined with an Eddy current damping. The STM is equipped with a tip exchange mechanism, allowing for in-situ preparation of the tips.