The Essential Knowledge Briefing practical guides under 'Gut Health in Early Life' examine gut health during the first 1000 days. These Briefings are specifically developed for healthcare professionals who work with infants and their caregivers. This Essential Knowledge Briefing practical guide, entitled 'Growth in Early Life: Growth Trajectory and Assessment Influencing Factors and Impact of Early Nutrition' provides an overview of physical growth during the first 1000 days from conception to the age of two years and the factors that influence growth. This Briefing also discusses growth challenges that can occur from compromised birth such as preterm, term small-for-gestational age and large-for-gestational age to growth deviations such as stunting and wasting, overweight and obesity in infancy and toddlerhood. The booklet is available to download in English.