Wash the yoghurt pot and either paint or cover in paper.
Glue on some eyes, a nose and a mouth to make a face.
Wet some scrunched-up kitchen roll and push this into the pot followed by a thin damp layer of cotton wool, leaving a gap of about 2cm below the top of the pot.
Sprinkle the cress seeds on top of the cotton wool, pressing them down lightly.
Leave the pot in a warm light place, check that the cotton wool remains damp and add a little water if necessary. Look daily for signs of growth, which should happen after about 7 days.
When the cress is fully grown (when it has green leafy tops) it can be cut and eaten straight away or you could put some in a sandwich or in a salad.