Histochemical examination of wheat kernels invaded by Aspergilli and Penicillia proved penetration of fungal mycelium into subaleurone and endosperm cells through aleurone layer cells. Walls of aleurone layer cells in invaded kernels were found to be thicker and split. Formation of spores in cleistothecia's in endosperm cells was found. The observation of kernels under a stereoscopic microscope was found to be a sensitive way to detect fungi invasion in cereal kernels.