a large plastic container (or sensory tub)
ping-pong balls (super cheap on Amazon)
water
red craft foam
Red water beads = Red Blood Cells (that carry oxygen)
Ping Pong Balls = White Blood Cells (that fight germs, bacteria, and viruses)
Craft Foam Pieces = Platelets (that help heal cuts)
Water = Plasma (helps the blood move through veins and arteries)