You can either harvest your microgreens just after their seed leaves or cotyledons appear or wait for them to put on a second set of leaves, known as true leaves. If the microgreens continue to grow beyond this, your crop will start to show signs of stress such as yellowing or become "leggy" (tall and unhealthy).
Pea shoots are one of the easiest greens to grow, even in a country as warm and humid as Singapore. My favourite pea variety is Sweet Peas because of their sweet flavour. The important thing to remember when growing pea shoots in Singapore is to keep your potting medium moist and to ensure your pea shoots get no more than 2-3 hours of morning sun. Beyond that, keep your tray/pot in a shaded spot.
Microgreens, unlike the full grown vegetable versions of the same seeds, provides an avenue for the home grower in Singapore a much faster, sustainable, and less expensive way of growing and eating your own food. Image your kitchen window sill, balcony, or an air well coming alive with trays lined with microgreens.