MgB2 is a promising superconductor for future applications to superconduct wires and tapes used at the liquid hydrogen temperature (20 K). Because the maximal superconducting current (critical current) in MgB2 depends on its microstructure, an "in-situ" process to fabricate MgB2 based on a reaction between Mg and B is effective in controlling the microstructure. However, the critical current in the fabricated MgB2 wires and tapes is not sufficiently high for practical use. This may be attributed to the imperfectness of the microstructural control in MgB2 wires and tapes. In this paper, we will discuss the microstructural features of MgB2 tapes fabricated using a typical in-situ powder-in-tube process. By observing the early stage of microstructural evolution in detail, we can gain insights into the next strategy for improving the microstructure of MgB2 tapes with respect to their applications.