Interphase is divided into three phases: Gap 1, Gap 2 and:

1. Interphase is the long preparatory period before a cell divides. 2. One of its three parts is where the DNA is copied. 3. Interphase is divided into three phases: Gap 1, DNA synthesis, and Gap 2. 4. DNA synthesis is the S phase, so S completes the set. _Source: OpenStax Biology for AP(R) Courses (CC BY 4.0), Ch 10 'Cell Reproduction', sections 10.1-10.5_