Caterpillars was a S.H.I.E.L.D. program led by Director Phil Coulson, which consisted in recruiting gifted individuals and helping them gain control over their powers. Graduates of the program joined the team Secret Warriors.
Phil Coulson and Andrew Garner developed an initiative to form a team of people with superpowers. Coulson handed Daisy Johnson a file about a new project codenamed "Caterpillars".
Andrew Garner was asked to assess psychologically Joey Gutierrez, an Inhuman whom Daisy Johnson wanted on the team. After the assessment, Garner deemed him unready because he did not have enough control over his power to melt metal. Disappointed by Garner's evaluation, Johnson explained the need for the team; Garner, calling them "Secret Warriors", understood her concerns, but noted that the safety of all S.H.I.E.L.D. agents had a higher priority than creating a team to make Inhumans feel more comfortable.
Johnson became upset at the organizational restraints which bound her when it came to her candidates in the Caterpillars program, especially when she discovered that Lincoln Campbell had a subcutaneous Tracker on him without her previous knowledge. She felt her position as the assembler of the team was being undermined. Phil Coulson tried to explain that the original idea of the program was to create a team of superpowered individuals to stay ahead of escalating problems; however, the creation of the Advanced Threat Containment Unit, the global outbreak of Inhumans, and their subsequent manhunt made him feel that he failed.
Alisha Whitley came to S.H.I.E.L.D. and Phil Coulson sent her double on a recruitment mission for Shane and Lori Henson; however, Lash killed the married couple first before the former killed Alisha's double.
Joey Gutierrez was transferred to the Cocoon where he gained control over his powers.
Deducting that Lash was a member of S.H.I.E.L.D., Lincoln Campbell contacted Alphonso Mackenzie and relayed his theory to him; Mackenzie agreed and brought Campbell to Zephyr One to tell Phil Coulson. Along with Daisy Johnson, the agents realized that Andrew Garner was Lash and went to Culver University to confront him and free Melinda May, whom he had captured. After Lash was captured and contained, Coulson offered Campbell membership in the Caterpillars and he agreed.
Acting as temporary director of S.H.I.E.L.D., Alphonso Mackenzie activated the Caterpillars project, officially making Joey Gutierrez and Lincoln Campbell agents, to utilize their powers in helping to mount an Attack on the HYDRA Castle.