Should you pick up knowledge like a sponge, a funnel, or a sieve? A sponge might soon be saturated and unable to pick up more, a funnel does not retain anything, a sieve separates the valuable from the superfluous. My goal is to make students find, enjoy, and retain many mathematical gems. Among my favorite topics are (elementary) number theory, (discrete and computational) geometry, matroid theory and applications, bioinformatics.