It is known that immersed boundary methods have the ability to handle complex geometries. A new immersed-boundary method for simulating flows over or inside complex geometries is developed by introducing a mass source/sink as well as a momentum forcing. Both momentum forcing and mass source/sink are applied on the body surface or inside the body to satisfy the no-slip boundary condition on the immersed boundary and also to satisfy the continuity for the cell containing the immersed boundary. Also, a heat source/sink is applied to satisfy the thermal conditions such as the iso-thermal and iso-heat flux conditions. To verify the accuracy of the present immersed boundary method, some numerical simulations would be shown. Finally, in this talk, based on the author"s personal research experience, some perspectives of immersed boundary methods would be presented.