When you emerge from the meteor, eat meat or plants to complete the "Eat" mission. You should grow in size. Keep eating until a cell eats another and reveals a gold shield. Swim into it and keep eating. Mate to equip the part in the gold shield. After you grow, find a "Booster" (red and have more than two eyes) and defeat it. This will unlock another gold shield. Swim into it and keep eating. After you grow again, find a cell that is leaving a pink trail. Defeat it and stay out of the trail. This will unlock another gold shield. Swim into it. Keep eating until you grow. Find a pink cell named "Pinky" or "Punky" and defeat it. This will unlock another gold shield. Swim into it. After you grow two times, find a "Buzzy" (orange). This will unlock another gold shield. Swim into it. Keep eating until you finish the Cell phase.