Homogeneous Catalysis occurs when the catalyst and the reactants are in the same physical phase.

• In biological systems, Enzymes (high molecular weight proteins) and their substrates are both typically dissolved in the aqueous cytoplasm or blood.
• Since they are in the same liquid phase, enzyme catalysis is a classic example of homogeneous catalysis.
• Note: Some consider it 'micro-heterogeneous' because enzymes have distinct active sites, but for JEE level, it is generally treated as homogeneous in the context of phase.