In a rare gathering, genomics met palaeontology at the 10^th New Phytologist Workshop on the ‘Origin and evolution of plants and their interactions with fungi’. An eclectic group of 17 experts met at The Natural History Museum (London, UK) on 9–10 September 2014 to discuss the latest findings on plant interactions with fungi (Eumycota) and oomycetes (Oomycota = Peronosporomycota), with topics ranging from the fossil record and comparative genomics to symbiosis and phytopathology. The discussions were largely disseminated via social media (Box 1). Highly diverse plant–fungal interactions have formed the backbone of land ecosystems and biogeochemical cycles since the Palaeozoic (see Fig. 1 for geological timeframe). As summarized by Christine Strullu-Derrien and Paul Kenrick (The Natural History Museum, London, UK) the first land plants arose c. 470 million years (Myr) ago (Kenrick et al., 2012; Edwards et al., 2014), at which time fungi and oomycetes had already colonized terrestrial ecosystems. Following their terrestrialization, these microbes began to abound within plant fossils (Taylor et al., 2014, and references therein). Ultimately, biological interactions sculpted the genomes of plants, fungi and oomycetes (e.g. Schmidt & Panstruga, 2011; Kohler et al., 2015). Here we illustrate the picture that has emerged from the discussions at the 10^th New Phytologist Workshop, and point to some pending questions.