When mankind came out of the caves and started agriculture, someone decided they wanted lettuce. Deliberately growing lettuce has been known for at least six thousand years. Perhaps it even grew in the garden of Eden. Lettuce is not a perennial but rather is grown each year from seed. It has a thick cell wall and milky juice which gives it the scientific name Lactuca sativa.
Whether it is iceberg, romaine, or a simple garden variety, people would find it hard to make a salad without using lettuce for the base.

Lettuce through the Ages

An earlier version of lettuce Lactuca Serriolas has leaves similar to the dandelion.

The Egyptian god of reproduction is associated with this variety of lettuce. Also, the Greek goddess of love Aphrodite is reputed to have put the slain Adonis in a lettuce bed, leading to the vegetable's association with food for the dead. Many civilizations around the world have used it for ritual or medicinal use. During the dark ages many believed you would find evil spirits lurking in a bed of lettuce.

The soporific effect of lettuce was featured in the 1909 story
The Flopsy Bunnies by Beatrix Potter.

Types

The main type one thinks of when thinking lettuce is head lettuce, but this is not the only type of lettuce.

The Most common types are:

• 
  Iceburg: A large crisp head lettuce with green leaves on the outside and whiter leaves on the inside. It is known for a crisp texture and a watery, mild taste.
• 
  Romaine: sporting deep green, long leaves with a crisp texture and deep taste. It is often sold with other salad greens.
• Little gem Lettuce
  A smaller, more compact variety of lettuce.
• Butterhead lettuce , including bib and Boston lettuce:
  this features a more loosely arranged head with large tender large leaves.
• Leaf: the first lettuce to ripen, it has broad, individual leaves. Some varieties come in different colors; also known as 'cut and come again' lettuce it offer a delicate taste and a slightly crisp texture. Best known varieties of leaf lettuce include green leaf and red leaf.

Planting

One researcher remembers how his dad loved to plant leaf lettuce. It was one of the first vegetable that matured and with a few radishes cut up and some Italian dressing made a nice spring salad. Time from sowing to eating is about six to ten weeks for leaf lettuce and about two months for head lettuce. If you have wildlife that likes to eat it before you do then you should invest in a fence or netting to protect the immature plants.

Harvesting

Leaf lettuces can be harvested a leaf at a time, or the entire plant can be cut with scissors just above the soil, allowing the plant to sprout new leaf growth. It is best to harvest only during the early morning hours and refrigerate until ready for use. Once the seed stalks start forming in early summer pull it out and replant as the leaves will be no longer young or sweet.
Head Lettuce on the other hand needs more time, and once the heads are the right size pull the whole plant, discard the roots and refrigerate.

Storage

All types of lettuce should be stored in a crisper or plastic container away from ethylene-producing fruits, such as apples, bananas and pears, since they will cause the lettuce leaves to brown. Iceberg or Romaine lettuce should stay crisp for a week. Butterhead or leaf lettuce wilts more quickly and should be used within a couple days.

Nutrition

Lettuce contains sizable amounts of fiber,Vitamin A, Vitamin C, and Vitamin K, as well as folic acid, manganese, and lesser amounts of many other nutrients. Many diets request that a person eat more fiber. In the colon, fiber regulates digestion and stimulates the production of bile, which in turn breaks down cholesterol.

USES

One widespread use of lettuce (along with other vegetables) is to make a sandwich look more healthy. Its the texture with the crunch that makes a burger deluxe and in the process it reduces the calories per gram.

Sometimes lettuce is mixed in with other greens like cilantro, lamb's lettuce , or radiccio. Many times it is sold unmixed, so that the user can decide what to add to it. Sometimes it will be served as a Caesar Salad or simply as a lettuce wedge salad.

Some ethnic foods like Mexican tacos use shredded lettuce.

Perhaps the lettuce has been in the refrigerator a few days and you want to try something different, why not cook the lettuce and use it as a side dish.  Another possibility is to make lettuce soup.