A Japanese woodblock print?

Red algae such as Antithamnion plumula are considered primitive algae. The red algae are classified in the division Rhodophyta, which consists of predominantly marine algae that are often found attached to coastal rocks.

Red human blood cells in Darkfield illumination

In bright field illumination red blood cells do not show a strong contrast. Staining is a way to overcome it. Dark field microscopy is another way to increase contrast. It is realized in a normal light microscope equipped with a special so-called dark field condenser, which prevents light passing through the lens, creating a dark field, unless light it is scattered by red blood cells (or anything else) present in the preparation.

The red blood cells in the blood bind oxygen to the red blood pigment