High-growth firms are rare and temporary, found in the upper range of firm growth. Human capital and innovation play a key role in their occurrence. Both human capital and research and development increase the chances of a firm becoming a high-growth one. Human capital boosts growth across all levels, reducing the likelihood of low growth. On the other hand, R&D not only raises the likelihood of high-growth firms but also of low-growth firms and exits, showing the risky nature of innovation. To support the growth of high-growth firms, policies should focus on enhancing both R&D and the quality of human capital.