Minichromosomes offer an enormous potential for plant breeding and biotechnology, because they may simultaneously transfer and stably express multiple genes. Segregating independently of their host chromosomes, they provide a platform for accelerating plant breeding. Minichromosomes can be established from cloned components in vivo (bottom up) or via engineering of natural chromosomes (top down). When they possess functional centromeres and telomeres, they should be stably inherited, but their meiotic transmission rate is below that of endogenous chromosomes. To achieve the customized generation and control the regular transmission of minichromosomes are important challenges for applied research in chromosome biology. Here, construction and biology of plant minichromosomes are compared with data available for yeast and animal systems.