Generally crystal surfaces grow below the roughening temperature. This implies that growth proceeds layer by layer involving steps. Therefore investigation of step patterns by microscopic methods and theoretical analysis is crucial for understanding crystal growth. In this review first several phase sensitive, optical microscopic methods and their use for the ex-situ and in-situ investigation of step patterns on (growing) crystal surfaces are described. Then the application of these optical methods to the surface examination of superconducting YBa₂Cu₃O_7-x, natural diamond and K₂Cr₂O₇ crystals is elaborated. In this emphasis is laid on the interpretation of the observed phenomena in terms of various models of crystal growth.