Sexual and asexual phases alternatively take place in the life cycle and this alternation between two phases is known as alternation of generation.
In plants, algae, and fungi alternation of generation is common.
It is not easy to observe however one or other phase is very small, even microscopic.
The sexual phase is called gametophyte generation, which produces gametes or sex cells, and the asexual phase, or sporophyte generation, produces spores asexually.
The gametophyte is haploid and has a single set of chromosomes and the sporophyte is diploid and has a double set of chromosomes.
In bryophytes, such as mosses and liverworts, the gametophyte is the dominant life phase but in angiosperms and gymnosperms, the sporophyte phase is more dominant.