Publication of the complete genome sequence of Arabidopsis thaliana, the first plant reference genome, in December 2000 heralded the beginning of the plant genome era. Over the past 20 years reference genomes have been generated for hundreds of plant species, spanning non-vascular to flowering plants. Releasing these plant genomes has dramatically advanced studies in all disciplines of plant biology. Importantly, multiple reference-level genomes have been generated for the major crops and their progenitors, enabling the creation of pan-genomes and exploration of domestication history and natural variations that can be adopted by modern crop breeding. We summarize the progress of plant genome sequencing and the challenges of sequencing more complex plant genomes and generating pan-genomes. Over the past 20 years the sequences of over 1000 plant genomes have been published, representing 788 different species with a high level of diversity.Long-read sequencing with novel scaffolding strategies has further revolutionized genome sequencing, enabling access to more chromosome-scale assemblies of plant species with increasing genome complexity and size.Citation trees for the first genome papers for Arabidopsis and rice illustrate substantial developments in plant genomics and a plant genome-enabled renaissance in all disciplines of plant biology over the past 20 years.Constructing near-complete genomes, assembling complex genomes, and building reference pan-genomes are some of the most challenges in future sequencing of plant genomes.