Heme is a porphyrin ring complex that contains a central iron atom. It's a key component of hemoglobin in red blood cells, which is responsible for carrying oxygen throughout the body. It's also found in myoglobin, which stores oxygen in muscles.

Here are some other important details about heme:

* Function: Heme binds to oxygen molecules, allowing red blood cells to transport oxygen from the lungs to the rest of the body.

* Structure: Heme is a porphyrin ring, which is a complex organic molecule with a central iron atom.

* Color: Heme gives blood its red color.

It's important to note that there are other iron-containing pigments, but heme is the most prominent one.