Induced pluripotent stem cells (iPSCs) are a type of stem cell created in a laboratory setting by reprogramming adult cells to an embryonic stem cell-like state. This is achieved by introducing specific genes important for maintaining the essential properties of embryonic stem cells. Unlike natural embryonic stem cells, iPSCs are generated from adult somatic cells (like skin or blood cells), circumventing the ethical issues associated with destroying embryos. iPSCs share many similarities with natural embryonic stem cells, including pluripotency – the ability to differentiate into almost any cell type. However, there are some differences. iPSCs may retain some genetic 'memory' of their tissue of origin, which can influence their behaviour and efficiency in differentiation. Additionally, the process of reprogramming cells to become iPSCs can introduce genetic abnormalities, raising concerns about their potential use in humans. Despite these challenges, iPSCs represent a significant breakthrough in stem cell research, offering a more ethical source of pluripotent cells for research and potential therapeutic uses.

Adult stem cells, while extremely valuable, generally have a narrower range of treatment applications compared to embryonic stem cells. This limitation is due to their multipotency - the ability to differentiate into a limited range of cell types, usually related to their tissue of origin. For instance, hematopoietic stem cells from bone marrow can develop into various types of blood cells but not into neurons or heart cells. In contrast, embryonic stem cells are pluripotent, meaning they can develop into nearly any cell type in the body. This versatility makes embryonic stem cells more suitable for a broader range of diseases, especially those requiring the regeneration of multiple types of tissue. However, advances in stem cell research, particularly in the field of induced pluripotent stem cells (iPSCs), are expanding the potential of adult stem cells, allowing them to be "reprogrammed" to an embryonic-like state and potentially widening their range of therapeutic applications.

Stem cells play a dual role in cancer research and treatment. On the research front, stem cells are used to study the mechanisms of cancer development. Cancer stem cells, a subset of cells within tumors, have properties similar to normal stem cells, including self-renewal and differentiation. By studying these cancer stem cells, researchers can gain insights into how cancers initiate, grow, and spread, which is crucial for developing more effective treatments. In terms of treatment, stem cells are instrumental in regenerative medicine, especially following cancer treatments that damage healthy tissues. For instance, hematopoietic stem cell transplantation is used to restore blood cell production after treatments like chemotherapy, which can severely deplete bone marrow cells. Moreover, research is ongoing into using stem cells to deliver targeted therapies directly to tumors, potentially reducing the side effects and increasing the efficacy of cancer treatments. This aspect of stem cell research is particularly promising, as it offers a way to target cancer cells more precisely while sparing healthy tissues.

Stem cells are fundamentally different from other cells in the body due to two key characteristics: unspecialisation and the ability to self-renew. Unlike specialised cells (like nerve cells or muscle cells), stem cells do not have specific roles or functions when they are first formed. They are essentially blank cells that have the potential to become any type of cell in the body. This unspecialisation is crucial because it gives stem cells the flexibility to develop into the various cell types needed for growth, repair, and regeneration. Additionally, stem cells possess the unique ability to undergo numerous cycles of cell division while maintaining their unspecialised state. This self-renewal capability is essential for replenishing and repairing tissues over a person's lifetime. In contrast, most other cells are specialised for specific functions and have a limited capacity for division and self-renewal.

The primary ethical concern with embryonic stem cells (ESCs) stems from the process of obtaining them. ESCs are harvested from embryos, typically four to five days post-fertilisation. This process inevitably leads to the destruction of the embryo, which raises significant moral questions. Many argue that embryos, as potential human life, have intrinsic value and rights, and thus their destruction for research or therapeutic purposes is ethically problematic. This perspective is particularly strong in groups with specific religious or moral beliefs about the sanctity of human life from the point of conception. The debate intensifies with considerations of when human life truly begins and whether the potential benefits of ESC research – such as curing debilitating diseases – justify the means of obtaining these cells. To address these concerns, scientists are exploring alternative methods, such as induced pluripotent stem cells, which do not involve the destruction of embryos.