A bottom-up approach is a strategy of information processing and knowledge ordering used in various fields, including software, humanistic and scientific theories, management, and organization. It is characterized by piecing together systems to give rise to more complex systems, making the original systems subsystems of the emergent system. In contrast, a top-down approach starts with the big picture and works down to the details.

Here are some examples of bottom-up approaches in different fields:

• Software development: Bottom-up emphasizes coding and early testing, which can begin as soon as the first module has been specified. Re-usability of code is one of the main benefits of a bottom-up approach.
• Investing: A bottom-up approach focuses its analysis on specific characteristics and micro attributes of an individual stock. In bottom-up investing, concentration is on business-by-business or sector-by-sector fundamentals.
• Project management: A bottom-up approach works by starting with individual components and building up to the larger system. It emphasizes breaking down a large problem or project into smaller, more manageable tasks and getting each individual task or component right before moving on to the next.
• Business management: Bottom-up communication revolves around the inclusion of all employees, their ideas, and their perceptions of the business to make the most informed decisions. Businesses leverage the bottom-up approach in an effort to produce the most comprehensive budget plan for all departments, resources, and employees.

The advantages of a bottom-up approach include flexibility, detail-oriented, and greater buy-in from team members. However, it can be difficult to dial in the right level of structure and guidance to give people, and its unclear how the different components of a problem or project fit together.