Several generations of soil microbiologists and plant pathologists have attempted to unravel the microbial composition, population dynamics and various life-sustaining processes in the soil. However, until recently, this basic resource for plant growth and nutrient recycling has to a large extent remained a black box. Studies have been made of the behavior of individual microorganisms or their population dynamics, but the relationship between the growth of individual organisms or parts of organisms (such as fungal hyphae) and that of populations and communities has been largely unknown. In particular, the spread of fungal colonies in soil has been an enigma, but now Bailey et al. (pp. 000–000 in this issue) have clearly demonstrated that spatial behavior of Rhizoctonia colonies can switch from finite to invasive expansion dependent on the non-linear relationship between the distance among substrate particles and the probability of colonization.