Which kingdom is known for organisms that have true nuclei and are usually multicellular?

The kingdom known for organisms that possess true nuclei and are typically multicellular is the Kingdom Plantae. Organisms within this kingdom, such as trees, flowers, and ferns, have complex cells that contain distinct nuclei, which house their genetic material. This characteristic is fundamental to eukaryotic organisms, distinguishing them from prokaryotic organisms like those found in Kingdom Monera, which lack true nuclei.

Additionally, multicellularity in plants allows for the specialization of cells and the formation of tissues and organs, enabling diverse functions and growth forms. While both Kingdom Fungi and Kingdom Animalia also consist of multicellular organisms and have true nuclei, the question specifically highlights the defining features of Kingdom Plantae.

Thus, the hallmark traits of true nuclei and generally multicellular structure point to the importance of the plant kingdom in the broader context of biological classification.