DUPLO is a LEGO theme intended for younger children aged one-and-a-half to six years old, and was introduced as a brand in the year 1975, though the name and the blocks had already been around since 1969. The Minifigures are a lot bigger.  The blocks are twice the length, width, and height of their equivalent System brick and half the length of a QUATRO brick. It can be noted that DUPLO is compatible with normal System bricks.
In 1977, the DUPLO name was dropped in favor of LEGO Preschool. This was used in the USA for a while, but it was brought back in 1979 when the first rabbit logo was introduced, as well as the first real DUPLO minifigures with movable limbs.
The name DUPLO was dropped again in favor of Explore in 2002. In the 2004 spring catalog there was a reminder that DUPLO was now called Explore, but later that year the well-known DUPLO name was back yet again.
First bricks (1969 - 1975) Edit
The first DUPLO bricks and the DUPLO name appeared in the year 1969. There were originally four colours; red, yellow, blue and white. They were designed to connect more with System bricks then the newer DUPLO bricks do. They were released in sets 510 and 511, both with System bricks. They were considered to be System-duplo sets, aimed at younger children. This was the beginning of the LEGO Groups products for the younger market. Two more sets were introduced the next year, adding blue and red wheel plates.
The sets were designed for 1-2 year-olds, but were continued to be mixed with System blocks.  In 1972, the first 2x2 studded brick was introduced.
When Duplo/Pre-School sets were introduced in their final form in 1969, the first DUPLO sets had a green LEGO logo. This logo was short lived, and by 1971 new DUPLO sets were introduced that used the red LEGO logo, and the text 'DUPLO' in green on the box'.
Start of the theme (1975-1980) Edit
In 1975 DUPLO became an independent theme, with five sets made up exclusively of DUPLO bricks. In 1977, the decision was taken to rename DUPLO Preschool. In the Preschool range, new DUPLO bricks where introduced, including archs and the first DUPLO figures, without movable limbs. In 1979, the theme was returned to the name DUPLO, and received its logo, a rabbit designed in a style similar to PRIMO's elephant. 
Continuation and new ideas (1980 - 2000) Edit
In 1983, DUPLO Figures were very similar to how they are today, with moveable limbs. They were more like larger minifigures than their predecessor, minus the ability to be taken apart, due to their target audience being young children. It also saw the first DUPLO Trains and the DUPLO Baby series.
In 1993, a grey-train rail system, 4.5v arrived. Since then there have been two others. Only two motorized sets were released in the DUPLO theme. In 1995, DUPLO Primo was launched. (DUPLO Baby in America) On the first of January in 1997, Primo and DUPLO were officially renamed LEGO DUPLO and LEGO PRIMO. 1999 saw licensed sets introduced to DUPLO, with Winnie the Pooh
Explore and licensed success (2000 to present) Edit
In 2002, the name was once again dropped, and the theme combined with LEGO Baby to form Explore, which tried to encourage children to explore life. In late 2004, however, Explore ended and DUPLO was once again back.
Themes of DUPLO Edit
Dacta DUPLO (1975 - 1977, 1979 - 2002, 2004 - present) Edit
- Main article: Dacta
Dacta or Educational DUPLO sets are those released under LEGO's educational brand, Dacta. They are often designed for schools and include things like LEGO tables.
Dacta DUPLO Subthemes Edit
- DUPLO Basic (Dacta)
- DUPLO Community
- Dino (Dacta)
- DUPLO Farm (Dacta)
- DUPLO Learning
- DUPLO Mosaic
- DUPLO Playhouse (Dacta)
- DUPLO Rattles (Dacta)
- DUPLO Supplementary (Dacta)
- DUPLO Toolo (Dacta)
- DUPLO Train (Dacta)
- DUPLO Zoo (Dacta)
- Explore (Dacta)
Town (1978) - (2003) Edit
- Main article: DUPLO Town
DUPLO Town sets were introduced in 1978. The sets ranged from fire and police to circus and race related sets. From 2004 The LEGO Group has used the name LEGO Ville for all DUPLO Town related sets.
Playhouse (1979-1980, 1982,1986, 1988, 1990-1998, 2000-2001, 2004, 2006, 2008, 2009) Edit
- Main article: Playhouse
Playhouse sets were introduced in 1979. The sets cover scenes from houses or single rooms to furniture sets for DUPLO Figures.
Train (1983 - 2002, 2005 - present) Edit
- Main article: Train (DUPLO)
DUPLO Train started in 1983 and is still active today. Thomas and Friends sets can be considered part of this theme. There have been three track varieties so far.
Baby (1983 - 1994) Edit
- Main article: Baby
Toolo (1992 - 1999) Edit
- Main article: Toolo
In Toolo, the pieces where held joined together using tools, like a screwdriver. 14 sets were released. A car based version, Action Wheelers, was released after Toolo ended.
Primo (1995 - 1996) Edit
- Main article: Primo
DUPLO Western (1998) Edit
- Main article: DUPLO Western
DUPLO Western sets were released in 1998. Eleven sets were released in this subtheme.
Dinosaurs (1998 - 1999) Edit
- Main article: Dino (Duplo)
A prehistoric based theme, Dinosaurs ran for two years. This theme was continued as Dino ten years later. Included were Dinosaurs and Cavemen.
Little Forest Friends (1999 - 2000) Edit
- Main article: Little Forest Friends
Little Forest Friends was based on people who lived in a forest and what goes on in their lives. It contained 12 sets, including a story book.
Winnie the Pooh (1999 - 2001, 2011) Edit
- Main article: Winnie the Pooh
Winnie the Pooh was the first LEGO and DUPLO licensed theme based on the Winnie the Pooh stories by AA Milne and the media based on them.
Action Wheelers (2000 - 2001) Edit
- Main article: Action Wheelers
Bob the Builder (2001 - 2002, 2004 - 2009) Edit
- Main article: Bob the Builder
One of the longest running licensed themes, Bob the Builder is based on the British children's TV show of the same name. It mainly featured the vehicles from the show. It became part of Explore when it was formed in 2002 and when DUPLO returned, Bob the Builder also returned with it.
Dolls (2001) Edit
- Main article: Dolls
Dolls was a 2001 attempt to get into the Doll market. There were nine regular sets available.
Zooters (2001) Edit
- Main article: Zooters
The theme of three sets, Zooters featured three named creatures. The theme only lasted a year.
Castle (2004 - 2008) Edit
- Main article: DUPLO Castle
Ferrari (2004) Edit
- Main article: Ferrari#DUPLO Sets
Two Ferrari DUPLO sets were released in 2004. They were similar to System releases.
LEGO Ville (2004 - present) Edit
- Main article: LEGO Ville
Farm (1979 - 198?, 1997-1999, 2010-present) Edit
- Main article: DUPLO Farm
Thomas and Friends (2005 - 2009) Edit
- Main article: Thomas & Friends
Thomas the Tank Engine and Friends is a theme based on the Thomas the Tank Engine books and TV show. It is closely related to Train.
Pirates (2006) Edit
- Main article: DUPLO Pirates
Four sets were released in the DUPLO equivalent of Pirates. The sets mainly contained ships.
Dino (2008) Edit
- Main article: Dino (Duplo)
Dino was an remake of the Dinosaurs theme from ten years earlier. The theme had twenty sets featuring different types of dinosaurs and DUPLO Figures.
Toy Story (2010 - present) Edit
- Main article: Toy Story#DUPLO sets
Cars (2010 - present) Edit
- Main article: Cars (Disney)
Other DUPLO Related Sets Edit
- DUPLO Ultimate Sticker Collection
DUPLO Games Edit
- GA06 DUPLO Memory Card Game 1
- GA08 DUPLO Little Forest Friends Counting Game
- GA12 DUPLO Toolo Memory Card Game
- GA13 DUPLO Learn and Play Look and Find Memory Card Game
- GA15 DUPLO Memory Card Game 2
Related Systems and Themes Edit
LEGO have also made other themes aimed at the younger children market.
- System-DUPLO; the origin of the DUPLO brick was here in 1969, when it was released with System sets before DUPLO became a theme.
- PreSchool was what DUPLO became in 1977, but by 1979 it was renamed DUPLO again.
- Baby, not to be confused with the DUPLO subtheme, was released originally as DUPLO Primo in 1995. In 1997 it became independent of the DUPLO theme, as Primo. In 2000, it was once again renamed to Baby. In 2002, it and DUPLO formed Explore. Baby ran again from 2004 and was discontinued in 2006
- Explore, an attempt to join together Baby and DUPLO as an all-compassing theme for younger children. With two years it was reverted back to the pre-2004 names.
- The word "DUPLO" comes from the Latin duplus, which means double.
- An average LEGO brick is able to connect to a DUPLO brick, and an average DUPLO brick can be connected to a Quatro brick.
- The DUPLO Figure can not be broken and rebuilt.
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