G07: Biology Cells: Types of Cells

The smallest unit of living matter that can exist by itself is the cell. Some organisms, such as bacteria, consist of only a single cell. Others, such as humans and oak trees, are composed of many billions of cells.

Stem cells are cells that have not differentiated, or become specialized. They are found in plants and animals, including humans.

STEM CELLS are the building blocks of the human body. At the start of life, they divide over and over again to create a full person from an embryo. As we age, they replenish cells in our blood, bone, skin and organs. Stem cells could be powerful tools in treating injury and illness.

Stem cells are seen as the keys to solving medicine’s most impossible puzzles, with the potential to heal the incurable, repair the unfixable, perhaps even stall the effects of aging. In 2004, Californians bet $3 billion on stem cell research in a first-of-its-kind bond measure. In this in-depth series, The Chronicle examines what’s become of that investment, and tells the stories of the patients, scientists and profit-seekers all banking on this miracle cell.