Minute particle with needlelike surface and its manufacturing method

The present invention provides an organic-inorganic composite microparticle containing a metal complex, which has multiple needle-like structures on the surface and includes the metal complex therein; and a method for producing the microparticle in a simple manner. By using a metal complex made from a polymer having a linear polyethyleneimine chain and a metal ion, a composite microparticle which has the metal complex in silica and has a micro-needle-like structures on the surface can be derived, thus a microparticle having needle-like structures on the surface is obtained, wherein there are nano-sized multiple needle-like structures on the surface of the microparticle. The needle-like structures on the surface and the spatial structure of the resulting microparticle can be controlled by varying the species of the metal ion and the types of the substrate medium for the metal complex.