Nuclear speckle refers to the distinct patterns observed within the nucleus of a cell when viewed under a microscope. These patterns arise from the organization of various molecules, such as proteins and RNA, which are involved in essential cellular processes like gene expression and DNA replication. The speckle structures are dynamic and can change in response to cellular conditions. They play a crucial role in the regulation of gene activity and the processing of RNA, making them important for understanding cellular function and development in organisms, including humans and other eukaryotes.