There are various applications of GFP, especially in molecular biology. It is used as a biological marker to visualize several cell types in animals, organs and tissues. GFP can be used as a reporter gene to monitor gene expression in different kinds of cells. For example, scientists use GFP to analyze cells in embryos and fetuses during development. GFP can also bind and glow to another protein, allowing biologists to identify that protein in an organic structure.
GFP can be used to study bacterial protein localization. GFP expression is highly sensitive and is used to visualize primary cellular functions like protein translation, DNA replication and signal transduction; the protein can label multi-components in a single cell.
Another application of GFP is its use as an active indicator of the surrounding environment or in organelles. Biosensors have also been made with GPP in modified forms. These modifications are  done from the phosphorylation sites of GFP in fluorescent molecules under specific conditions. The GFP engineered with potassium channel is the first biosensor to be encoded in a membrane.
Another application is that GFP can be used as a fusion tag; the GFP gene is fused with the gene encoding the target protein and expressed in the cell. This can be done at the amino or carboxyl terminus of a protein. The fused protein keeps its function as well as its fluorescence from the GFP, and major cell organelles can be tagged successfully.
Lastly, GFP is used for host-pathogen research. It acts as a biological tracer that allows for the analysis of the colonization, proliferation, and spread of pathogens in animals.