We are exploiting both well-established and innovative approaches to define the genetic interaction network underpinning 3D growth in Physcomitrium patens. In this moss, which is a representative of the earliest evolving land plants, 3D growth is preceded by an extended 2D filamentous growth phase. Given that 3D growth is a defining feature of all land plants, and arose as part of the adaptive transition from water to land, our research will answer one of the most fundamental questions in biology – how was terrestrial life established?