Identify and correlate the main techniques used in assisted human reproduction, including the manipulation and cryopreservation of gametes and embryos, as well as low and high complexity techniques in assisted reproduction.

\text{1. In vitro fertilization (IVF):} This is a high complexity technique where eggs are fertilized by sperm outside the body.

\text{2. Intracytoplasmic sperm injection (ICSI):} Also high complexity, where a single sperm is injected directly into an egg.

\text{3. Cryopreservation of gametes and embryos:} High complexity, involving the freezing of sperm, eggs, or embryos for later use.

\text{4. Preimplantation genetic screening (PGS) / Preimplantation genetic diagnosis (PGD):} High complexity techniques used for detecting genetic defects in embryos before implantation.

\text{5. Gamete intrafallopian transfer (GIFT) and zygote intrafallopian transfer (ZIFT):} These can be considered lower complexity compared to IVF and ICSI, involving the placement of sperm and eggs (GIFT) or a fertilized egg (ZIFT) into the fallopian tubes.

**Answer: A detailed break-down and classification of assisted reproductive techniques**